/sqt/ - stupid questions thread

What is coordination number of copper in [Cu(gly)2(H2O)] supposed to be? I get 5 but supposedly it should be 6.

Gly is bidentate so 2x2 = 4 + 1 from monodentate H2O = 5

What am I missing?

Does
[math]\frac{x^{2}-1}{x-1}[/math]
equal
[math]x+1[/math] ?

>>8230663
Unless x equals 1, yes. If x equals 1, the first expression is undefined.

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>>8230668
Damn it. You just foiled my plan.

Why do I get little blister/wart things on my fingers when I touch unpainted metal (aluminum?) handrails on public transit?

Would post a picture, but they're too small to see.

>>8230671
There are such things as allergies to specific metals. You may want to check with your doctor.

>>8230688
Heavy exposure to members of the onion/garlic family does it too (as I understand it, to everyone). And by heavy, I mean like dicing ten pounds of shallots.

But the absolute worst is the combination of the two: touching metal with onion juice on my hands. Fingers swell and turn red, pain is so intense I can't grip anything. So I thought it might be some kind of aluminum/acid reaction.

>>8230610
Anybody?

>>8230694
>So I thought it might be some kind of aluminum/acid reaction.
I don't think aluminium allergy is common, and I don't think aliminium is commonly used for guardrails either (too expensive).

Could it be nickel that you're allergic to? That's reasonably common, I believe. Of course, your doctor will know.

One of my friends is one of those 'flat earthers', and we often debate about it. His latest quarrel is that
1. a spaceships hull should be turn to shreds in space (vacuum)
2. the sun's radiation is wavelengths and since space has no atoms, the wavelengths should not be able to travel.

How do I debate this? I was reading up on photons but I don't really understand it.

>>8230716
>1. a spaceships hull should be turn to shreds in space (vacuum)
Why?

>2. the sun's radiation is wavelengths and since space has no atoms, the wavelengths should not be able to travel.
That is not how photons work. This confusion was a major topic in the physics research of the early 1900s, and it's kinda complicated, but the upshot is that photons are NOT like waves in a pond that rely on a carrier material (in this case, water).

>>8230722
Does mommy know your on the PC?

>>8230749
>your
Does you're mummy know?

>>8230722

1. Vacuum = extremely low density. As such he argues that matter in outerspace should be ripped apart and spread evenly, just as it would on earth. If part of earth's lower atmosphere becomes lower or higher, it corrects itself (that's what wind is from). Ever tried to suck air out of a bottle?

2. Radiation travels through vibrating atoms/molecules at certain frequencies and amplitudes. How does it travel through space?

>>8230753
NASA has a vacuum chamber and it isn't ripped apart

>>8230759

I have a penis that is 100 inches long. If you give me a couple billion dollars I could prove it to you with photos and a cheap video

So I'm taking general relativity next semester.

What am I in for? How difficult can it be?

>>8230753
>Vacuum = extremely low density. As such he argues that matter in outerspace should be ripped apart and spread evenly, just as it would on earth.
A strong rigid container can sustain different pressures on the inside and the outside. A typical submarine, which has a very strong hull, keeps its internal pressure at 1 bar, and can dive to a depth with an outside pressure of some 50 bar; if it goes deeper than that, the pressure difference will crush the sub. A spaceship would have an inside pressure of 1 bar, and an outside pressure of 0 bar (vacuum), which is very tame in comparison with the sub (only 1 bar of pressure difference instead of 50 bar). Even aircraft at cruising heights have only 0.25 bar of outside pressure (air pressure is substantially lower at that height) and 1 bar inside pressure, meaning they could almost-if-not-quite sustain the pressure difference of a spaceship.

If you shake a coke bottle, it will build up an internal pressure of over 3 bar (which is why it will spray in your face if you open it carelessly). You'll note that the coke bottle does not explode, with an internal pressure of 3 bar and an outside pressure of 1 bar (sea level atmospheric pressure), and thus 2 bar of pressure difference. The spaceship in the vacuum of space has only 1 bar of pressure difference, meaning it could sustain it even when built to the strength of a coke bottle.

>Radiation travels through vibrating atoms/molecules at certain frequencies and amplitudes.
Not really. Radiation travels through space; when it hits an atom, it gets absorbed, and then possibly-but-not-necessarily re-emitted. That's what causes phenomena like refraction.

>>8230771

but 0 bar is infinitely less pressure then 1, to the point where it would utterly consume and tear about any matter that enters it. And pressure and density IS what determines temperature. Apart from completely decompressing and pulling apart a spaceship, it should evaporate it too while it distributes the pressure (and density) among space.

2. Radiation doesn't get absorbed by an atom. Radiation IS wavelengths, It isn't a physical entity, it is the MOVEMENT of atoms.

What is the best basic math teacher online outside of khanacademy?

>>8230779
>but 0 bar is infinitely less pressure then 1, to the point where it would utterly consume and tear about any matter that enters it.
No, it isn't.

A fluid (gas or liquid) at a certain pressure in an enclose applies a certain force to the enclosure. This force is proportional to the amount of pressure. When there are pressures on two sides of an enclosure, the inverse forces on the enclosure cancel out, and what's left over is the force of the difference between the pressures.

This is a *difference*, not a ratio or something. If there is 20 bar of pressure outside a coke bottle and 21 bar inside it, that's just the same as 10 bar outside and 11 bar inside, or 0 bar (vacuum) outside and 1 bar inside. In all cases, the pressure difference on the bottle is 1 bar, and if the container can sustain a 1 bar force without breaking in some way (exploding or rupturing when the inside pressure is greater than the outside pressure; imploding or rupturing when the outside pressure is greater), it's a situation that can sustain itself.

Where the vacuum part DOES matter is what happens when the enclosure DOES break. If a gas container has 21 bar internal pressure and 20 bar outside pressure, and the container ruptures, the resulting reaction will be far less violent than when the same thing happens to container with 1 bar internal pressure and 0 bar outside pressure. But this difference only comes into play when the enclosure breaks; as long as the enclosure is intact, 21:20 versus 1:0 are identical, in that the container has to sustain a 1 bar pressure difference.

>Radiation IS wavelengths, It isn't a physical entity, it is the MOVEMENT of atoms.
No. That is NOT what radiation is.

How do you get rid of social awkwardness, low self esteem, depression...

when I lay on my ear for a longer time(sleep) and then when i get up it's aching like hell. It doesnt hurt if i don't move, otherwise it's unbearable. I feel the pain only from outside the ear, like the cartilage in the ear is hurting. Why? Just stupidly grown nerves?

>>8230609
Has anyone ever used "Master the Content"? It's a website you pay for and it has resources to study for all board exams like MCAT, OAT, etc. It has full lectures, labs, and questions. I want to get t because I'm preparing for the MCAT and I'm not really liking the Kaplan books because they are too condensed Anyone have resources that are good for someone with a weak base in physics and chem? If anyone has any or gives me their reviews on master the content thank you. I appreciate it

This will not be a stupid question, but a stupid series of two posts about the stupid math in the stupid-but-fun movie "Cube".

The number of primes less than or equal to 999 (or, equivalently, less than or equal to 1,000) is 168. This is given by the prime counting function π(1000) = 168.

In the film "Cube", three-digit base-10 numbers give information on (in addition to being a coordinate system) whether given cubic rooms are equipped with a deadly booby trap. Every room has three three-digit base-10 numbers, ranging from 000 through 999. If any one of a room's three-digit numbers is a /prime/ number, or more strongly if any of these three-digit numbers is a /power/ of a prime (which of course includes the primes themselves), then that room contains a booby trap which must be avoided. The trouble is that the characters only have their brains, and the clothes on their backs to work with, to do calculations.

So the question becomes, how many of the numbers from 000 through 999 are powers of primes?

First of all, since we are fortunately not trapped in the cube and have access to a computer, and since π(1000) = π(999) = 168, there are exactly 168 prime numbers less than or equal to 999 - of course, each prime is also a "prime power" in that the exponent is simply 1. We must therefore simply add to these 168 prime numbers, all of the composite natural powers of primes which remain less than or equal to 999.

1/2

What is the realistic maximum temperature the Earth would peak at due to uncontrolled global warming?

Are there any good guides to doing a good final year Physics research project?
Or maybe the blog of someone who did one and got a good grade.

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>>8230846

The amount of trial and error involved is /obviously/ minimal, and we have merely to compile a small table of numbers. A sensible approach is to establish an upper bound for which no natural power higher than 1 of a prime will produce a number less than 1000, and work backwards. Consider that the square root of 1000 is in the low thirties somewhere (we don't care exactly where). Furthermore, 37^2 = 1369, while 31^2 = 961. We therefore easily establish that 31, is the largest prime for which a power greater than 1 is yet less than 1000. The problem reduces to raising the first 11 primes to powers until they exceed 1000, and discarding those last results. Furthermore 2, the smallest prime, when raised to the tenth power produces 1024, which just exceeds 1000 - the point being that 9 is the largest exponent that we need consider, in any event. We establish another upper bound to make our work easier.

The practical upshot is that there are exactly 25 composite numbers which are integer powers of primes being less than 1000. Therfore, the final answer to our original question is 168+25 = 193.

Now, about the movie: the female math student Leaven has no trouble determining whether a given three-digit number is itself prime or composite. And yet toward the end when it is realized that powers of primes are also entailed along the above lines, she throws a hissy fit claiming that the work entailed is "astronomical". But as we've just seen, a few elementary observations cut the work down to size in very short order, and in fact the number of composite powers of primes is much smaller than the number of primes. For some reason, the autistic savant Kazan is needed to discover these numbers. The point being that it is absurd that Leaven, who is competent with a fairly complex mental task, is yet unable to make simple observations to attack what turns out to be, in a sense, a much simpler mental task.

It turns out that Leaven is the one who really "sucks at math".

>>8230716
>'flat earthers'
I don't know how this has anything to do with the questions you asked, but I'll give a qualitative answer to what you asked anyway.

>1. a spaceships hull should be turn to shreds in space (vacuum)
HY-80 is a high-tensile strength alloy steel, which has a yield (effective maximum) strength of 80,000 psi (550 MPa) (see: Wikipedia article)
The deepest that a submarine has ever dived is about 10.9 Km down, at that depth the pressure is about
101325(atmospheric pressure)+[seawaterdensity][grav accel][depth] = 110MPa
That's about 1082 Times the pressure that you and I feel at sea level!
Qualitatively, you can probably see that your friends proposal is ludicrous, seeing as we can build vessels that can survive 1082X atmospheric pressure. So we can definitely craft one that can survive 1X atmosphere. (Note that the vessel in space would only have to survive against the pressure difference inside the cab (atmospheric, since humans must be inside), and the zero pressure outside of the vessel (space)).

>2. The sun's radiation is wavelengths and since space has no atoms, the wavelengths should not be able to travel.
One of the properties of electromagnetic waves is that they need no medium in which to travel, as a matter of fact, mediums generally take energy away from the wave that travels through them. Lets think about it, suppose that we need a medium for light to travel, then wouldn't that mean that any vacuum space should appear totally dark? Taking a few minutes to look up vacuum chambers, we know that this in not the case, therefor your friend is certainly wrong.

I can take the time to explain some more, but I think this will do. If your friend tries to refute you, just tell him to read a book on the history of physics, perform some of the experiments related to these topics, and see if he can prove himself right. (he can't)

Mates, why does combining for ex. two linear equations (y=kx+l) solve for their intersect? I understand if you have y=3x+2 and y=4x-2, two equations with two unknowns, and you can solve for their combined x and y and get their intersect point coords,

I just don't understand why it works. The point's coordinates would have to agree with both equations independently, but I just don't understand why it works when I combine them both. Could someone clearly explain it in a simple way?

I have OCD and if I don't understand every nuance of math, it kills me slowly from the inside.

>>8231055
If you have a linear equation, or more generally a functional equation (some equation of the form y = f(x)), it describes a curve consisting of all the points (x, y) satisfying the equation -- that is, all points (x, y) such that y = f(x).

If you have two curves, their intersection is the set of points that are on both curves. So for two curves defined by functions y = f(x) and y = g(x), their intersection is the set of points for which both equation holds; that is, the set of points (x, y) such that y = f(x) and y = g(x).

For linear equations, the intersection consists either of the full function (if f and g are identical), is empty (if f and g differ by a constant), or consists of a single point (in all other cases). For functions in general, the intersection can consist of arbitrary number of points. For example, if f(x) = 3 and g(x) = x^2, the intersection between the curves y = f(x) and y = g(x) consists of all the points (x, y) such that y = f(x) and y = g(x), that is, all points (x, y) such that y = x^2 = 3.

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Okay, I've been a lazy cünt during hs, and after it ended, I took a gap year to learn hs math so that I can do engineering or physics in the end on uni.

Now, I've been studying all grades of HS math for a duration of 6 or so months, and I've gone through all of it. I watched YT vids of a professor solve and explain HS math without really practising each topic too extensively (basically he would explain the concepts needed and lay down the formulae, then proceed to solve around 10 problems for each topic).

Now that I have a math test in a month (Matura) I wish to refresh everything I've gone through, how would I go best about it, of course without rewatching all the videos again? I now have a much more concrete understanding of math, and of course from all the vids that I've watched, I have retained the general understanding of all topics and can even derive most of the formulae. I just need to quickly go over everything once again, without consuming too much time. I've got a month to do so.

>>8231085
Thanks, dude.

>>8230671
>>8230694
Type IV hypersensitivity reaction.

>>8231164
is there a list of topics on the test? post them here

>>8230663
it equals f(x) = x+1 if x is not 1, and is undefined otherwise (piecewise!)

>>8230609
Will I see this become safely implementable in my lifetime?

http://www.foregen.org/

I read this somewhere (don't be a faggots about it if you find out where)

"You'll eventually understand WHAT math is. It's not just calculating and shit. It's the language of recognition of patterns in EVERYTHING that we do as humans and everything around us.
It's how we as humans interpret the universe. It's all we have! So just keep that in mind. It's the persistence of mankind's thirst for knowledge.
If you think of it like that, and want to understand the world and question everything around you beyond I believe in what everyone else tells me."

Could anyone elaborate on what he means? I'm kind of struggling with math, I mean I'm doing my best to learn it, but I'm not fond of it nor have a natural aptitude imo. I love what physics stands for, explaining anything and everything, why is the sky blue, why does the sun shine, what photons are etc. I love it. But I'm bad at math (currently, still trying to get better at it) and unfortunately due to past experiences, scared of it.

How do I overcome this?

How to I make LaTeX give me flat blocks of color, cell-by-cell, completely shading a given cell or entry, in a matrix-like or tabular environment?

I don't care what the table-environment is, exactly (as long as it can render a very large table). What I care about is that I can point to any one cell, or entry, and simply plug-and-chug the color of my choise in that cell, totally filling the "whitespace" of the cell.

cursory searching on this topic has already brought up the color and xcolor packages, and there are even options ot color different /rows/ to improve readability. I need to drill down to cell-by-cell.

>>8231196
Well, there isn't really a list of topics as it is a general high school maths knowledge test, so basically all grades of high school math in one test.

>>8230609
I'm doing Honors Chem in high school next year. What should I expect?

Also, my friends were all surprised that I got a higher grade in my Biology class than my English class. I don't understand why it's that surprising.

>>8231309
Mathematics is the sum of knowledge that can be gained without observing the world. For example, in physics you HAVE to do experiments and studies and collect evidence, otherwise there's no correlation between your thoughts and the real world. However in math none of that matters. In math whatever you come up with is true no matter where in the universe you are, and even if the universe were different. For example you can imagine a universe where gravity follows an inverse cube law instead, or where elephants don't exist. All of math is still true there, but not all of physics is. Math holds true in any universe.

Moreover, math is the study of abstracting complexity. For example, a coin flip is pretty complex. There's all this physics and chemistry of nickel and other metals, interacting with the atmosphere and various particles in the air, and so on. Math lets us abstract this away into a probability of 1/2 on each side. Now that we've done this, we can use the same math for a coin flip to talk about the probability of getting an even number on a die, because we took the time to do abstraction.

Mathematics is not discovered. It is invented by humans, and it turns out humans want to learn about the universe, so the math they invent usually helps understand the universe. Everything is math.

None of this will help you with your math studies, other than motivation. If you want more advice you'll need to expand on your current knowledge and what you want to learn and why.

>>8231315
does this go up to algebra 2? That might be only a US-thing though

what's the highest level of math you learned? factoring quadratics? graphing inverse trig functions? proof by induction? calculus?

>>8231179
Holy shit I think you're right.Thanks!

What happens if you stick a negative time value into an n-body equation?

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>>8230609
Suppose I have some E. Coli...

Can they remain dormant at 14 degrees Fahrenheit? I want to start growing my own at my crib, I just need time to get the materials together (petri dishes, gelatin, beef powder, etc). Speaking of, where the hell can I find Agar powder? I'll use Gelatin otherwise. Oh, and I need a poor mans incubator. I was thinking a rice cooker, one where you can set the temperature.

Answers/suggestions/info much appreciated, help me become the E. Coli whisperer. I'll keep you guys posted if this pans out.

>>8231500
Nothing spectacular. I haven't taken graduate level mechanics yet which is typically when you encounter such issues, but it's not like a negative time value is going to break many equations unless standard mathematical bullshit makes it (e.g. if the equation contains sqrt(t)), then you get a nonsensical answer. Typically we aren't concerned with negative time values. We usually just call the beginning of observation of system 0, but it can be shifted to suit convenience.

>>8230751
>Does you're mummy know?
=
>Does you are mummy know?
Learn to speak english

why dont i have wisdom teeth but alot of other people i know do?

>>8231741
14 F you might get lucky, but it's not a sure fire thing. As for growing them, E. Coli will grow on pretty much anything, so you should be fine without agar. For your incubator, your oven would be decent, or just a cooler with a hot water bottle in it.

>>8231913
I was thinking more about gravitational things.
e.g. T=-5 in a three body equation. Would it cause things to fly apart?

>>8231440
Limits and derivatives come last, and then something more after it, not all that interesting.

>>8231313
I suck at table environments, but I think this might work. http://tex.stackexchange.com/questions/50349/color-only-a-cell-of-a-table

>>8231362
Is mathematics actually invented? So are you saying that [math]1 + 1 = 2[/math] isn't an intrinsic truth (if you are talking about the abstract notion of putting one and one together)?

Why are prime numbers considered the 'building blocks' of natural numbers?

>>8232139
Mathematics exists only in our heads. 1 + 1 = 2 for no reason other than because thats how we define them. Generally we try to base our math in axioms that reflect the real world, but not always and even when we do theres no way to prove those axioms are correct

What if 'one' is not 'equal to' 'one'?

>>8232020
Sweet. I think the E. Coli I have may have spores in them, so they should be good to stay in my freezer for the time being. Thanks anon

>>8232446
Every natural number can be written as the product of prime numbers.

This is a very important fact in number theory and wildly used in encryption.

>>8232491
That would violate certain axioms.
If you are constructing the natural numbers you usually base it on set theory.
"One" is defined as the "set of the empty set" which by the Axiom of extensionality means that it is equal to the "set of the empty set" which was defined to be 1.
So "one" is always equal to "one".

But if you could provide a true proof that "one" does not equal "one" the concept of set theory and most mathematics would break down together with it.

>>8232138

Thank you very much for the link, I appreciate it.

>>8232446

Not only what this guy has already said, but >>8232899 even more importantly, every natural number has a /unique/ representation as a product of primes. There's a bijection from the one representation of numbers to the other - a bijection is a fancy way of saying that everything in one set has exactly one buddy that it pairs off with in the other set, and everyone has a buddy in the other set, with nothing left over or doubled up in either set.

>>8232138

I want you know that this solved my problem. Stupidly, I spent two days trying to figure out how to color in a fucking box in LaTeX and I just wasn't getting the right link (and not for lack of trying on my part), cheers.

Is there any legit reason to care about [math]L^p[/math] spaces with 0<p<1?

My PhD advisor is dropping hints that he's planning to start a spin-off company soon and would like me to join him.

Thoughts on these sorts of arrangements?

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Does anyone know where to find a pdf of this book?

Is arccotangent ever used for anything? Have you ever used this function for anything other than textbook exercises that teach inverse trig functions?

We use positive and negative to refer to numbers larger and smaller than zero.

Is there a similar term for ratios or fractions larger or smaller than one? Like if you had a workplace and were measuring the male to female employee gender ratio, is there a word like "a positive ratio"?

>>8233977
larger ratio and smaller ratio?

Remember, rigorously defined, probability ratios (odds) are not the same as fractions.

How vital is "working memory" within a university?

I feel this question doesn't deserve its own thread since I'm guessing it's been discussed before. Here goes:

I recently watched Ex Machina with a friend. Afterwards, we discussed AI and I said I didn't believe 'true' AI (i.e., machine capable of producing original ideas rather than simulating them) was possible. My friend fiercely opposed this (he's a compsci faggot) but used shitty arguments.

What do y'all think? Personally, I can't foresee it since we don't even understand the complexity of the brain, much less how to create a computer that behaves as a brain.

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Why is this wrong?

>>8234014
I totally agree with you. No machine can do something is isn't programmed to do, never will it develop its own ideas (they don't even have ideas they're not rational, they're machines) , unless in some way they are programmed to say/do that thing. Claiming a machine can have free will is bullshit

>>8234181
It's not. I suppose you could go even further and divide the second factor by two, if it's a website giving you trouble.

You in HS, or just trying to learn basic algebra?

>>8234014
If it exists in nature, it can be replicated in a lab (eventually)
Saying it's not is defeatism.

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An object in uniform circular motion has its acceleration vectors always pointing to the center of a circle.

What about an ellipse? The planets are in elliptical orbits around the sun and their acceleration vector is principally towards one of their foci, the one at the sun. But the generic ellipse defined by the parametric equation c(t) = (acost , bsint) has an acceleration vector that points towards the origin of the plane, not one of its foci (unless a=b=1 in which case its a circle).

What gives? Also is there a path parameritization for planetary orbits or ellipses with acceleration vector always pointing to one foci?

>>8230704
Aren't plenty of people allergic to aluminum? I always hear about it in deodorants with insane itching and redness.

>>8234181
I think if you do what >>8234198 mentions, you get 3y-5 twice and so could write that expression squared to further simplify it (maybe that's what your electronic homework is trying to get you to do).

What should I major in if I want to do something with studying sound? More specifically, audio quality. Electrical engineering?

Why do radioactive particles damage living things?

I tried asking my teacher and the response I got was "they have a lot of energy and that's bad"

>>8234374
that's pretty much it. gamma ray emission is bad because the photons are energetic enough to penetrate into your essential cell components and break up their chemical bonds. The particle emissions, like neutrons, are bad because it can bombard your cells--fucking up the nuclear structure in things like your DNA. The body has adapted to handle low-energy, atomic foreign invaders or visible light with some UV exposure from the sun. It doesn't have effective methods to shield vital cell reproductive components against the emissions from radioactive particles.

>>8234382

Ah, cool. Do the particle radiations also penetrate due to energy or quantum tunnelling? I know they're not as energetic as gamma.

can you prove a theorem is impossible to prove?

>>8234468

You should look into Gödel for more on this type of thing.

EXTREME CAUTION: Due to the abstract nature and the historical significance of his most important statements, Gödel has apparently been misrepresented on a constant basis by internet debaters since the 1990s. Extreme care, willingness to research primary and secondary documents, and critical thought are required when actually discussing the content of Gödel's ideas.

Directly to your point, I state that Gödel's incompleteness theorem can be fairly represented as saying that /there exist/ theorems which are unprovable, whereas your language suggests a specific theorem. I am of little help in discerning between the two situations. You should check wiki and look around for other views on same.

while here, there is also a "completeness theorem" which people like to cite, to feel rounded-out:

https://en.wikipedia.org/wiki/G%C3%B6del%27s_completeness_theorem

What's so special about the quantity
[math]\int R\sqrt{-g}d^{n}x[/math]

where the integral is taken over an n-dimensional Riemannian manifold, R is the Ricci scalar, and g is the determinate of the metric?

I know this is (proportional to) the Einstein-Hilbert Action in the vacuum and invariance of this action results in the field equations, but I'm trying to understand why the quantity is important enough to differential geometry to suppose that it be invariant in the first place.

>>8234468
Can nothing be proven?

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How the hell do you get from the starting equation to the next part? I understand the sequence is being used as a regular function but where did 1/x on the bottom come from?

>>8234494
The first n.

1/(1/x) = x

given function f strictly increasing in R for which it holds that f(x)<g(x)

prove that (fof)(x)<(gog)(x), x in R

>>8234572
But the exponent should change as well, if you make the simple substitution x := 1/n.

>>8234490
things have been proven, so somethings can

>>8234468
[math]\exists M: {\rm I\!N} \precnsim M \precnsim {\rm I\!R}[/math]

Which very roughly means that a set exists that is smaller then the real numbers and bigger then the natural numbers.

Gödel proved in 1938 that this claim cant be disproven and Paul Cohen in 1963 that a proof is also impossible.

But keep in Mind that the things Gödel did is mathematics beyond the level of what we ordinary humans can understand.

>>8234468
For some theorems, you can. For some it is provable that you can't know whether a proof exists or not.

>>8234490
In the "real" world nothing can be 100% proven. In math, whether explicitly or implicitly you ALWAYS make statements like "If [conditions] are true then [statement] is true." You always start from axioms. Whether the axioms are true or not in reality is undecidable but that doesn't change the correctness of the statement "if... then ...".

>>8234494
I don't get the second equal sign. Where did the sum go.

So ( 1 - e^-1/x ) / (1/x) = -1/x * ( 1 - e^-1/x ) / (-1/x2) = ( 1/x * e^-1/x - 1/x ) / (-1/x2) and then what?

>>8230716
> 1. a spaceships hull should be turn to shreds in space (vacuum)

Maybe this helps: A space ship is basically a closed metal box, with high pressurized air inside and less pressure outside. We have similar situations on earth, e.g. a bottle of helium for baloons. Because the metal likes to stick together, the bottle doesn't explode, although the helium inside is under pressure. Same for the space ship, plain and simple. Gas would disperse, because the atoms have velocity in random directions. But since they collide, with the stable wall, they can't. The force of impact on the bottles' surface is the pressure.

>2. the sun's radiation is wavelengths and since space has no atoms, the wavelengths should not be able to travel. If he believes in helium bottles, the believes in spaceships.

> 2. Radiation travels through vibrating atoms/molecules at certain frequencies and amplitudes. How does it travel through space?

Propagation of radiation is a fundamental property of space itself. Space IS the medium and it DOES get distorted like water by a water wave. Every type of energy density (e.g. em-radiation, black holes, stars, planets, single atoms, his ignorant ass) can propagate and distort space. This has been proven again and again since Einstein and GPS, mobile phones and much more wouldn't work if it wasn't so. Radiation does not need atoms to travel.

>>8232127
>>8231315
>>8231164
BUMB!!

What good is knowledge for beside from employment rate and better pay?

proton guns.That is all.

>>8231164
Revision papers. Good practice and easy to see where your weaknesses lie.

Why the fuck has it been so humid in Los Angeles lately?

I want to talk about history here because anons here at least care about scientifical method instead of baiting for a living.

>>8234203
Those equations do draw out an ellipse, but with them you assume the instantaneous speed of an object in orbit is constant. In real orbits, the sun pulling on something with an extremely elliptical orbit like a comet, the comet slows down at far distances from the sun, skewing the acceleration vector towards the sun. Remember Kepler's laws, the rate of area swept out by an object in orbit is constant with time. This means the orbit must slow down at farther distances and speed up at closer distances to the barycenter (in this case, the sun). Search google for the solution to the two body problem if you want a parameterization for the position vector. Not sure if there is one. The orbits of the planets are extremely close to a circle and constant speed, though.

>>8233843
I think trigonometric substitution within integrals of the form 1/sqrt(a^2+x^2) (sorry, can't into LaTeX), although you can and normally just use tangent. If you can't solve the integral exactly however, the Taylor series expansion approximation might lead you to choose one over the other for simplicity, I guess. I remember using tangent more often in calculus, though. There may be problems inherent in the domains and ranges of the inverse functions that make you choose one over the other. I can't remember if it matters though.

Who is an electrical engineer here?

Question: If I have a decently coupled primary and secondary in a current transformer, do I need to worry about magnetic saturation of the core if I never open circuit the secondary? I'm just trying to transform the impedance of the load to be able to give it more power. What I'm asking is, can I use as little wire as possible to achieve the turns ratio needed to transform the impedance?

>>8234675
Okay true. I just remember I had saved last year's tests and a whole bunch of problems that were in the preceding tests.

Would I be able to get a basic understanding of high school physics in a time little longer than one month (deadline for the test), if I have a solid understanding of high school math, and physics seems intuitive to me? (have to decide will I even take the test or not until tomorrow)

Thanks!

>>8234873
You say that the instantaneous speed of the equation is constant, I assume you mean the one with c(t) = (acost , bsint) I gave. But the vector norm of c'(t) is root( (acost)^2 + (bsint)^2). How is this constant?

My question's purpose is to prove Kepler's laws and so I would like to stray away from using them if possible.

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what steps comprise these syntheses? this quiz isn't supposed to be covering our chapter on alcohol reactions, just alkenes and alkynes (and substitution/elimination reactions as needed)

i'm so shit at these questions.

>>8235014
Nvm, it's not constant, my bad. My point is your parametric equation does not represent THE two body time-dependent position vector, even though it is a position vector. What I mean is they both are ellipses, but yours is not a solution to the two-body problem.

With your equation, if you divide the magnitude of the acceleration with the magnitude of position you'll see it is a constant ratio of 1. The acceleration is high when the distance from the center is high, which would give two points of high acceleration, the ends the major axis. This does not follow Kepler's laws or any inverse square of the distance from center of body force equation.

>>8230610
Wtf is gly? A sugar?

>>8230671
Metal splinters. No, they don't come out, only go in farther

>>8234204
Aluminum flakes are added to antiperspirant deoderant sticks with the intention of clogging the pores and literally stopping perspiration. Linked to cancer (carcinogenic). That itchy redness is BS made up by advertising dollars in the millions.

>>8234942
I'd say sure. Physics 1 is pretty straight forward and there's gotta be a bajillion resources online for it. Get determined, anon.

>>8230716
See which one of you two survives a college hard science.

>>8230749
>your
Does mommy know you're on the PC?

>>8230803
Try coming up with (making) jokes
Go in the woods and scream!
"You can never, ever
Hide your heart
Don't ever try
If you don't give your heart wings
You'll never, ever Fly"

>>8234657
If you desire money you go for it.

>>8234942
Try and see.

>>8234203
> Also is there a path parameritization for planetary orbits or ellipses with acceleration vector always pointing to one foci?

There isn't a closed-form expression for a Kepler orbit, i.e. x and y (or radius and angle) as functions of time.

You need to find the eccentric anomaly E from the mean anomaly M by solving Kepler's equation:

E - epsilon * sin(E) = M

Typically, you'd use Newton's method.

>>8234489
You can look for gauss-bonnet theorem. It's a generalization of that fact.

You might also note that you have to deal not with Riemannian but with pseudo-Riemannian manifolds (= your inner-product doesn't have to be positive-definite).

https://en.wikipedia.org/wiki/Pseudo-Riemannian_manifold
https://en.wikipedia.org/wiki/Gauss%E2%80%93Bonnet_theorem

>>8233749
Yes. gen.lib.rus.ec.

http://gen.lib.rus.ec/search.php?req=quantum+computation+nielsen&lg_topic=libgen&open=0&view=simple&res=25&phrase=1&column=def
here it is.

>>8233435
Don't think so. It's not even a normed space for 0<p<1 since the triangle inequality reverses.

>>8235125
So heres a follow up to another thread I made. Given that a series of bodies, all with a common focus, are moving in ellipses, and these bodies satisfy the conclusion of keplers third law, then is it possible just from this information to prove that the acceleration vector of these bodies is pointing to this common foci, as opposed to somewhere else. from what you post and what others post, the answer would seem to be no, but jsut to make sure

>>8232107
Oh, that depends on the scope of the gravitational interaction you're looking at. For instance, if you're examining an equation for a system calculating its time evolution from a beginning where the planets are already in orbit, then no, it would probably just cause them to precess backwards. However, if you're talking about a system where an object flies in (from effectively infinitely far away) and becomes ensnared in another objects gravitational field, then yeah, running the equation backwards would cause the object to fly apart.

>>8234385
Nope. They usually just fly through the empty space in your atomic structure, bumping into things until they lose all their energy and get stuck. The average penetration depth of different particles is different and known as the Bragg Peak.

>>8235391
Not really sure. Deducing the inverse square law, I imagine Newton's thought process went something like this:

We have Kepler's laws.
Planet orbits are really close to a circle, which is a special case of an ellipse.
Kepler's third law is orbital period squared is proportional to semi major axis cubed (distance from sun cubed).
Uniform circular motion acceleration a = 4*(pi^2)*r/(T^2) and thus T^2 = 4*(pi^2)*r/a.
Kepler's third law T^2 is proportional to r^3.
Therefore (some constant)*r^3 = 4*(pi^2)*r/a.
Therefore a = (some constant)/(r^2).
Knew really massive things are hard to accelerate/move, saw apple falling etc.
Deduces F = m*a.
Knew falling rate doesn't depend on mass.
Gravity must only depend on other bodies mass.
Therefore Fg = (some constant)*M*m/(r^2).
Proceed to solve the two-body problem and confirm orbits are indeed ellipses.

>>8235381
Site's blocked in Bongland

Can anyone rehost it on Zippyshare or something? I don't imagine it'll be a big file.

>>8235381
>>8235581
Scratch that, used ZenMate and it worked

CHEERS
R

>>8235581
http://rgho.st/6W26YFs27
But you might use proxy as well

>>8235391
> Given that a series of bodies, all with a common focus, are moving in ellipses, and these bodies satisfy the conclusion of keplers third law, then is it possible just from this information to prove that the acceleration vector of these bodies is pointing to this common foci
Not based solely upon those constraints.

Consider the hypothesis that orbits are defined by the parametric equations
x(t) = a*cos(w*t)
y(t) = b*sin(w*t)

Then:
x''(t) = -w^2*a*cos(w*t)
y''(t) = -w^2*b*sin(w*t)

I.e. [x''(t),y''(t)] = -w^2*[x(t),y(t)].

IOW, the acceleration vector always points toward the centre of the ellipse. This is true regardless of w (= 2*pi divided by the orbital period).

Note that in this hypothesis, the eccentric anomaly is equal to the mean anomaly. In reality, this is only true for circular orbits.

tl;dr: Kepler's first and third laws aren't sufficient. You also need the second law.

what kind of jobs can i get with only a bachelors in math? I don't like programming or teaching. should i look at another major?

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>>8235170
glycine
pic related

Is the PhD student life really as depressing as people on here say? Or does it seem that way because the people who don't like it just come here to bitch?

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Ok, i'm trying to understand how does RSA algorithm does work.

i have to clarify that i have elementary education level.

Prime numbers
p=5
q=7

N is the product
n=5*7=35
n=35


phi(n)=(p-1)(q-1)=
phi(35)=(5-1)(7-1)=24
phi(n)=24


now here's my problem

the dude said that now we have to find
e= a prime relative number between 1 and 24
e will be the public key.

But how do i find it?

>>8235663
Likely the latter. I'm about to start a PhD, just finished a master's. A master's isn't as intense but I can relate to why some lament over their PhD work, sometimes shit just doesn't run smoothly. Talking to other PhD's and post-docs, seems like it's more a matter of how passionate you are about what you're doing.

>>8235655
The only job off the top of my head which doesn't involving programming or teaching would be an actuary.

If a 500lb object with a length of 6ft and a width of 2ft hit an island head on from above at 100,000miles/second (forgive the non-metric), how much damage would that do to the island? I know it's about 700megatons of tnt worth of energy, but that doesn't really help.

Writing a story and need help with this scene. Currently I have the object not only demolishing that island, but the shockwave from the impact sweeping away everything on the surface of neighboring islands. Is this accurate?

>>8235943
>I know it's about 700megatons of tnt worth of energy, but that doesn't really help.
I should clarify. I've found sources telling me what a bomb with that much energy would do in terms of making a crater, but it's not really 1:1 in terms of damage since that's heat energy centered about 1,000ft in the air (if I remember how far up nukes detonate at) while what I'm looking for is the damage from kinetic energy.

>>8234657

Pleasure. I personally derive pleasure from knowing things which interest me, and I think it is fair to say that this is a common item in the human experience.

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I'm trying to follow this proof (pic related), and I'm confused about a particular claim at the end:
>It follows, whether a is the immediate successor of one of its predecessors or the supremum of them all, that s(a) is similar to an ordinal number.
I can see how the the statement follows if a is an immediate successor, but I can't figure out how it follows when a is the supremum of s(a).

Here's what I have so far. We let [math]f: s(a) \to \mathcal{C}[/math], where [math]\mathcal[/math] is the collection of ordinals similar to initial segments of [math]s(a)[/math], and [math]f[/math] has the property [math]s(x) \sim f(x)[/math] for all [math]x \in s(a)[/math]. By our assumption that [math] a = \sup s(a)[/math], it's possible to show [math]\mathcal{C} = \bigcup \mathcal{C}[/math], and thus [math]\mathcal{C}[/math] is an ordinal.

My claim is that [math]f[/math] is a similarity from [math]s(a)][/math] to [math]\mathcal{C}[/math], but I'm having trouble actually showing this. Does anyone have any ideas?

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Why do "women in stem" insist of plastering their ugly mugs on every fucking picture stem related?

>>8236280
>im here for the science, not for the bitches

>>8236286
>disregard females, acquire science

>>8234489
Hm, sorry, that >>8235373 answer is just not right.

This action is not an invariant in general. It [b]is[/b] invariant in case of 2-dimensional manifold however.

What I thought to be a topological invariant following from Gauss-Bonnet theorem is this https://en.wikipedia.org/wiki/Gauss%E2%80%93Bonnet_gravity You can see that term G is much more complicated than just Ricci scalar.

So your question remains to me too. I don't understand why Einstein-Hilbert action is a thing to be minimized. :(

Looking at the equations for determining orbital speed, I got really confused about the old "which object falls to the ground faster" experiment. Let's say we drop an elephant and a feather at the same time. Ignoring drag, wouldn't the elephant fall faster, because the pull the elephant exerts on the earth is bigger than that of the feather? Obviously the difference would be so small that you wouldn't notice, but it would still be there right?

>>8235774
Choose a prime which isn't a divisor of phi(n).

>>8236497
Keys generated by openssh typically use 65537 as the exponent.

I'm not sure what happens if this is a divisor of phi(n), i.e. whether it chooses a new exponent or chooses new primes.

what's the difference between LED's and [regular diodes]?

I'm reading through Dennery and Krzywicki's Mathematics for Physicists, and I'm sad that the book doesn't include problems.

Is there a good book or something to accompany this text, which does include problems to work?

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What am I doing wrong? I solved for three separate values of u added them together and my solution meets all the conditions, but it's apparently incorrect?

Is Khan Acedemy enough for understanding high school physics at a decent level?

>>8230609
I have to wait to a weekday to see my ortho, wanna help me understand my x-ray results?

Wrist X-Ray:
FINDINGS:

There is a minimally displaced fracture of the ulnar styloid. At the
radius, no discrete fracture line is confidently appreciated. No
discrete carpal bone fracture is identified. Alignment at the carpus is
normal.

IMPRESSION:

Minimally displaced ulnar styloid fracture. A distal radius fracture is
not clearly identified.

Elbow X-Ray:
FINDINGS: Osseous alignment is within normal limits. There is
effusion/hemarthrosis. On the oblique view, there is irregularity at the
radial margin of the radial head, highly suspicious for nondisplaced
fracture. A fracture line cannot be identified on the other views.

IMPRESSION:

Nondisplaced radial head fracture.

So are they gonna put me in a cast past my elbow?

>>8236667
Regular diodes don't emit light.

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>>8233435
>>8235389
In the spirit of the delightful book Counterexamples in Topology I made a Venn diagram based on Rudin's FA chapter 1.
I have no idea if they are good for anything besides being a counterexample to that the venn diagram can be collapsed in a certain way.

>>8236793
It says use separation of variables to get a product solution.

I get:
u(x,y) = 5 * e^((20*x^2+72*x)/45) * e^(-(16*y^2+24*y)/45)

Which I've confirmed satisfies both the PDE and both boundary conditions (I'm assuming that u[x] is the partial derivative of u wrt x).

>>8237058
If you don't mind could you explain how you got that answer?

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>>8236793
You added them together. [math]u[/math] is supposed to be the product of two pure functions.

>>8237061
Separation of variables.

Put u(x,y)=c*A(x)*B(y)
du/dx = c*A'(x)*B(y)
du/dy = c*A(x)*B'(y)

(4y+3)*(du/dx) + (5x+9)*(du/dy) = 0
(4y+3)*c*A'(x)*B(y) + (5x+9)*c*A(x)*B'(y) = 0
A'(x)/A(x)/(5x+9) = -B'(y)/B(y)/(4y+3)

LHS depends only on x, RHS depends only on y, so each side is equal to some constant k.

A'(x)/A(x)/(5x+9) = k
A'(x) = k*A(x)*(5x+9)
A(x) = C*e^(k*(5*x^2/2+9*x))

-B'(y)/B(y)/(4y+3) = k
B'(y) = -k*B(y)*(4y+3)
B(y) = C*e^(-k*(2*y^2+3*y))

=> u(x,y)=c*e^(k*(5*x^2/2+9*x))*e^(-k*(2*y^2+3*y))
u(0,0) = c so u(0,0)=5 => c=5

differentiate wrt x:
u[x](x,y) = k*(5x+9)*u(x,y)
u[x](0,0) = k*9*5 = 45*k
u[x](0,0) = 8 => 45*k=8 => k=8/45

Can anybody just share their opinion on the validity of IQ test and the meaning of such number.

I dont know much, just what I heard, that it actually means nothing and doesnt accurately describe how intelligent a person is. But how true is this?

Are IQ test and IQ in general approved by science?

pls respond

>>8237180
A long time ago some old white guys administered a large number of tests attempting to measure what they considered to be mental skills and then they analyzed the resulting data. Then one of the tests was selected for best being able to explain the results on the other tests. This test was given the name "IQ test." A high or low IQ test score does not imply that your other mental skills are strong or poor. On the other hand, people with high or low IQ test scores are observed to do better or worse on those other tests of mental skills on average.

>>8237233
go away racist cis white male

>>8235663
It really depends on how your project goes and what your supervisor is like. Personally I'm enjoying it but I'm easy going, my supervisors other student went a bit crazy at the end because they're both fucking stubborn. I've known other people who've quit and most of the time that is because their supervisor is a dick. Occasionally someone's project completely falls apart and that is hell but quite rare.

>>8236493
>>8236493
>>8236493
>>8236493
anyone?

>>8231320
High school = joke
You should get an A, or you literally aren't trying

Would Khan Acedemy be enough for understanding high school physics at a decent level?

>>8236493
There was a thread about this a week or two ago.
Remember that this experiment historically is not done with millimeter precision
The two famous ones being Galilleo (Before forces and Newton's law of universal gravitation) and one of the Apollo missions.

https://warosu.org/sci/thread/S8191577

Can one take a class at a different community college while on probation at a different community college?

>>8237316

I think so, I mean its not like you wont learn something new, who knows maybe you'll came up on different sources along the way.

My approach would be to start doing it right now but be open to considerate other sources (perhaps a text book) or series of tutorials / videos.

>>8237323
There seems to be no agreement in the thread about whether or not the bowling ball would fall faster.

Looking at the formulas for orbital equations, the masses of both the object orbiting and the object being orbited are added together in the formula, which means bigger object needs to move faster to maintain the same orbit. Doesn't that also dictate that the bowling ball should fall faster, even if we don't have the precision to see it? To make it extreme, if we dropped an elephant and an object with the same mass as the earth, onto the earth, would that object not accelerate ~twice that of the elephant, with earth as the reference frame?

>>8232010
Whoosh

>>8231362
What if you are in a universe where a coin flip is not 50/50? If such a place exists..

>>8236982
boop medfags

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I was messing with some shapes and numbers and ran into this identity. Does it mean anything or is it just trivial? Does it show up anywhere?

>>8237373
I've been thinking about how to answer this rigorously and I can't be assed to, but consider these examples. First make the assumption that no mass is gained in the Earth system. Next consider 2 extreme situations: 1. where the mass of the falling object is infinitesimal in comparison to the Earth's, 1 and 2. where the mass of the falling object is half the Earth and the Earth now has half its mass.

Now in the first situation, the falling object's acceleration is just G(M Earth)/r^2 and the Earth's acceleration is essentially negligible. So it falls at the "normal" rate. Now consider the second situation where the masses are equal to 1/2 Earth mass. In the center of mass frame, the acceleration on the "falling" object is G*(1/2*M)/r^2, 1/2 that of the normal acceleration. However in this situation the Earth (or what's left of it) is also accelerating at G*(1/2*M)/r^2 and so its acceleration is equal to that of the falling object. The resultant velocities would also be equal and opposite. If you consider falling to be relative to the Earth's frame, in the Earth's frame of reference the falling object has twice the speed than in the center of mass's frame of reference. And so it goes:

a(Earth frame) = d(v Earth frame)/dt = d(2*v center of mass frame)/dt = 2*d(v center of mass frame)/dt = 2*a(center of mass frame) = 2*G*(1/2*M)/r^2 = G*M/r^2

Which is equal to the "normal" acceleration we are used to. Off the top of my head, I'm not sure how to confirm if the fractional masses in between these two extremes lead to the same conclusion.

However, if you drop an elephant and a feather at the same time, how fast they fall depends on how far apart they are. If they are right next to each other the Earth moves up towards each and they hit the ground at practically the same time. If they are at the opposite ends of the Earth, technically the elephant hits first because it attracts the Earth more than the feather does.

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Electricity follows the path of least resistance. Consider the pic attached. Ignoring the white background, the red has slightly more resistance than the green material and the white block has practically 0 resistance and the black dots are negative/positive terminals. Assuming that having to pass through a little bit of red is easier than having to pass through a lot of green, would the electricity just go straight up or would it follow the green material all the way around? My idea is that at any given point, the current "decides" which direction to go, so it would never pass through the red because it doesn't "know" that there is no resistance on the other side so it "thinks" the green path is the easiest. Sorry for the quotes, not sure what other way to describe it.

>>8237804
Small-angle approximation. For small x, sin(x) ~= x. For large N, x/N will be small and sin(x/N) ~= x/N.

>>8237815
> Electricity follows the path of least resistance.
Electricity follows all paths. Given multiple paths between two points, the current along each path is inversely proportional to the resistance along that path.

Given your example, if the resistivity of the red is only slightly more than that of the green, most of the current will go through the white area.

You can obtain a fairly accurate solution by finite element analysis (i.e. approximate the system by a grid of resistors, use Kirchhoff's laws to create a system of linear equations, then solve it).

>>8237004
how do they not emit light?

>>8237815
I suppose you have the wrong way of approaching this.

It has nothing to do with what the electron "sees", its path is due to the landscape it travels through.
Let me give you an analogy:
Suppose one of your terminals is at the top of a hill, while the other one is at the foot of the hill. Now, given your picture, think of the different colors as the steepness of the hill when going from top to bottom (red being a little steep, green being medium steep and white being very steep). Now, suppose that the terminal at the top of the hill is a tap of water, while the terminal at the bottom is a drain. If the water starts to flow, and depending on how much of it comes out of the tap, which way will it take?

>>8236450
Thanks, I appreciate the response. There must be some proper argument for why the Einstein-Hilbert action is invariant with respect to the metric. I'll find it eventually.

>>8234014
>>8234188
dont listen to this guy.

this may help you understand the nature of ai
https://en.wikipedia.org/wiki/Intelligent_agent

>>8238031
Indirect band gap.

>>8237815
>Electricity follows the path of least resistance.
I want to do horrible things to the person who invented this meme.

>>8237074
Take your pedophile cartoons back to >>>/a/.

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Is it really better to formulate anything in categorical language?

Should we define groups as 1-object categories where all morphisms are isomorphisms? How should we define vector spaces, manifolds, integrals then? Is there any sense to this?

>>8238350
>>8238350
what did he mean by this?

>>8230610
you have to account for 2 water molecules ie: 2 H20 not one

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>>8234615
explain

why do we like to smell our own fart but not others ?

>>8238559
http://lmgtfy.com/?q=indirect+band+gap

>>8230846
>>8230861
You posted this on /tv/ the other day, yeah?

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how do I get this silver plating off the inside of this Erlenmeyer flask? I haven't tried anything yet - it has been on there for a long long time.

>>8238754
forgot to mention I have only house hold items to spare. No access to a lab or concentrated chemicals.

>>8237119
Thank you very much for your help

>>8238580
At first seems counter intuitive, but there is a way to say that one infinite set is bigger then another infinite set.

Consider what we mean when we say that two finite sets have the same size.
You could say they have the same amount of elements because we can assign every element of set A one element of set B.

This idea can be extended to infinite sets and we say to infinite sets are equal if there exists some rule that assigns every element of set A exactly one element of set B.

For example consider the set A={1,2,3,...} and B={2,4,6,...}.
They have the same size because if we take one element from A and multiply it by 2 we get an element from set B.
Two things are important here, firstly this element is unique, so if we take two different elements from set A and multiply them by 2 we have to different elements from set B and secondly if we double every element from set A we will at some point get every element of set B.
These two properties of the rule "multiplying by 2" means that it is called bijective.
And 2 sets are equal if there exists such an bijective rule between them.

For example the set of all natural numbers and the set of Integers are equal, but surprisingly there is also an bijective rule between the set of natural numbers and the ration numbers.
So there exists a way to assign every rational number one natural number but importantly there exists no such rule for the real and natural number which means that the set of the real numbers is bigger then the set of all natural numbers.

The question now is is there a set which is bigger then the natural numbers but smaller then real numbers?

This is exactly what:
[math]\exists M: {\rm I\!N} \precnsim M \precnsim {\rm I\!R}[/math]
means.

This question has been proven to be neither provable nor disprovable and is one example of where the incompleteness theorem manifests. That means that you could not construct such as set but you also cant prove that such a set does not exists.

>>8238964
>bigger then the natural numbers but smaller then real numbers

0.5, 1, 1.5, 2, 2.5, 3...

I once saw somebody reply here with the name of a physics book that was considered the ''bible of physics'' or one of the best sources for somebody that wished to self study and learn.

Does this description ring a bell?

>>8238996
No that is not true the set {0.5,1,1.5,...} has the same amount of elements as the natural numbers.

That was what i was trying to explain.

Take the function f(x)=0.5*x which is bijective.

If you take a natural number and apply it to the function f(x) you will get a unique number from your set and if you do this for every natural number you will get every element of your set.

That means that your set and the set of the natural numbers are equal.

There also exists such a function between the natural and rational numbers but not between the natural and the real numbers

Besides that it has been proven by Gödel that you cant construct such a set that is bigger then the natural numbers but smaller then real numbers.

>>8238996
"Bigger than" and "same size" are just provocative terms used when discussing infinite cardinalities. Stop using your intuition and follow definitions.

>>8230610
The water forms two co-ordinate bonds

How are ore deposits mapped?

>>8240273
There's a bunch of techniques. Look up geophysical imaging.

Do you think id be disadvantaged if i did a course in Mathematical and Computer Sciences as a 3 year course, compared to doing a double degree in mathematical sciences + computer sciences which would probably equal 4-5 years?

Is there a way to opt out of class presentations for college without losing your grade? Mom is trying to make me go to college but the mere thought of presentating to a class is making me want to kill myself.

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>>8240482
sorry but this is one of the most pathetic things ive read

>>8240482
grow a fucking backbone you moron. There are brilliant people not able to go to college because of the conditions they live in and you want to quit because you have to talk in front of a group.

I know a lot of people say this as a joke on this website and the internet as a whole, but are you actually fucking autistic? are you so socially inept that the thought of talking in front of others makes piss dribble down your leg? maybe you should just kill yourself. no really, please die and free up some space for other more deserving humans.

>>8240482
If you take courses your enthusiastic about a lot of the fear goes away and your excitement for what your presenting takes over.

>>8239024
S := set of natural numbers
M={0.5}
S combined with M

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i'm trying to wrap my head around the process of reprojecting 3D points that have been acquired through a reflection from a first surface mirror

how am I going to do this? autocad isn't friendly with individual points, when I import the cloud it acts as a whole object rather than thousands of individual points

>>8238696

Yes I did, to much greater success on that particular board, although the thread was eventually given over to stupidity which I participated in. I was half-surprised it wasn't deleted.

I know regression to the mean is a thing, but is the mean moving up or down? Is it somehow staying in place?

>>8240537
You... haven't taken set theory, yet, have you?

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What is the most effective way to convert mechanical force from an electric motor to thrust if the primary limitation is how much area it takes up? Efficiency and torque or rpm requirements aren't much of an issue, just getting the maximum thrust out of a small blade/compressor is what I want to find out.

Volume isn't so much of an issue so much as how much space is used when in operation, with helicopter blades being the worst option.

>>8240599
let me clarify this picture for anybody who's seen it

the red lines are connections from origin to the corners of a plane which acts as the reflective surface, the blue lines are the rays that are reflected from the mirror, thereby creating a field where reflected points are to be reprojected

it's hard to comprehend this because i don't have any data available with reflective information and i'm trying to determine if it's technically feasible using the software available to me (autodesk)

http://hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html

Why do the Weak and Strong forces have finite range?

Quick probability question, I'm probably being stupid but I want to make sure this makes sense.

Let [math]X[/math] be a nondegenerate random variable. If we have the bound
[math]\Pr[X \leq a] \leq p,[/math]
does this necessarily imply
[math]\Pr[X \geq a] \geq 1-p ?[/math]

>>8230609
why does 1=2 ?

>>8240671
You just posted your answer. A ducted fan. the duct prevents a lot of the efficiency loss meaning the fan is still useful at smaller swept areas.

>>8241157
P(X>a)>= (1-p)
But otherwise yes

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How do I solve this limit without using L'Hopital's?

>>8241244
conjugate?

>>8241232
good point, thanks

>>8241267
Can you explain or write the solution please?

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>>8241271
>>8241289
hope it's good

>>8240868
The weak force has finite range because the gauge bosons that mediate the interactions (W,Z) are massive. For information on why mass limits the range of the force, see
https://en.wikipedia.org/wiki/Yukawa_potential

The strong force gauge bosons (gluons) are not massive, but the limited range of the force can be understood through color confinement.
https://en.wikipedia.org/wiki/Color_confinement

>>8241289
Remember in algebra quadratics like x^2 - 4? You could expand them like so: (x - 2)(x + 2). Well, pretend the numerator of your limit is one of those factors (it would be the analog of x - 2 in my example above). So, multiply the top and bottom by the "conjugate," which finishes the quadratic. So, in this case, you'd multiply by sqrt(x + h) + sqrt(x)

>>8230609
Is it incorrect to say that if you were to graph a simple multiple regression with 3 or more beta coefficients, that the regression is "taking place in 4 dimensional space", or am I just too high and stupid?

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If anyone could please help me with a couple of questions here, I would appreciate it.
a. I know from a derivation that the initial wavepacket equation can be simplified to Ae^((-x^2)/4α^2), but I don't know what x is or how to find A. Would x be 1?
b. Would this just be the same thing but using a nonzero value of t such that the result is 10 times the result of the position uncertainty in part a, then use that value of t to find the momentum's uncertainty?

I am not a smart math person, I've been able to program a video game using very basic math.

I have this open game where you can, from the get go, go to any dungeon you want. There are 8 dungeons in the game. Purely for retro nostalgia-sake, I'm going with a password system (that I've already made and implemented)

Here's the thing though, I need to write a unique password for every combination of dungeons that have been completed that are possible. I've realized that I'm going to have to make up a shit load of passwords because there are a lot of possible combinations.

If you just beat one dungeon, that's eight possible codes right there (one for each of the eight). Then, if you beat two dungeons, that's every combination of two of the eight. Three, every combination of three of the eight, and so on until there's just a single password necessary that represents all eight dungeons beaten (and gives immediate access to the final dungeon)

The thing is. I remember being taught how to find the total number of numbers in a span of numbers like this wayyyy back in Middle School, but I've completely forgotten and I'm worried that if I just start writing a table of combinations myself that I'm going to miss one or two. I need to know how to get every combination with assurance that I'm not missing a single one.

>>8241974
x is your position. In order to find A, sorry but you're going to have to integrate that horror and usually if it comes out nicely you're left with some squared fraction which means that A is just that fraction but inverted + under a square root radical.

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>>8241999
Pardon me asking this, but how would that give you A? Have I done it correctly in this photo? Or are you saying that A would just be √π/α = 3544907702

>>8241994
me.

Also, order doesn't matter. If you beat dungeon 2 and then 1 in that matter, it's the exact same as if you beat 1 and then 2. So [1, 2] and [2,1] are the same and I do not need separate passwords for them.

>>8241994
> There are 8 dungeons in the game.

> there are a lot of possible combinations.
2^8 = 256 combinations, to be precise. Or 255 if you skip the password for "zero dungeons completed".

> I need to know how to get every combination with assurance that I'm not missing a single one.
Binary.
00000000 = 0
00000001 = 1
00000010 = 2
00000011 = 3
00000100 = 4
00000101 = 5
00000110 = 6
00000111 = 7
00001000 = 8
...
11111110 = 254
11111111 = 255

Each combination is a number between 0 and 255 inclusive. If that number is x, then in any C-like language, the expression (x>>i)&1 returns bit i of x (where i is between 0 and 7 inclusive).

>>8241994
You have 2^8=256 possible passwords. Minus one, if you don't have a password for the start of the game with zero dungeons solved. Minus another one if you don't have a password for the end of the game with all dungeons solved.

Instead of hand-designed passwords, you want to design a system here where your password just encodes 8 bits somehow. The trick being that users must not be able to guess the passwords, of course.

>>8241974
there's a nice formula for integrating functions which involve e to the power of f(y) where f(y) is quadratic. I don't remember it anymore, haven't done quantum in a while, but you should look it up. it'll save you a lot of time. anyways. you find A by integrating that and setting it equal to 1. it must equal 1 because it's a probability, which is why A is the normalization constant.

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>>8242088
>>8242089
well... I have my work cut out for me.

I bet in the gameboy era they were smart enough to just reference hex values and make this all infinitely more simple.

Here's the way feeble mind came up with doing a password system. I made a 5x5 grid. when you hit the OK button on a square it appends a number value to a password array. When you're done, you go to the DONE square and it'll check if your array matches a correct password array that I've already written.

My way totally works, but now I have to write 255 unique passwords completely manually.

Is it still 255 unique passwords after the information I've given you here? >>8242081 How [1,2] is identical to [2,1]. I'm using the set() function that doesn't care about order, so if the password is 1,2,3,4,5, you can input 5,4,3,2,1 (with the blocks) and the password will work.

>>8242123
>Is it still 255 unique passwords after the information I've given you here?
Yes. You have 8 boolean variables (one per dungeon) that can all independently take on 2 possible values (solved or not solved), so there are 2^8 possible states.

>>8242134
Just out of curiosity, how many possible passwords can there be with my 5x5 grid? I can make passwords as short as a single block or using all 25 blocks. If it's too complexity/work, you don't have to tell me, I'm already positive that there are vastly more than 255 different ways I can fill these blocks, so I'm not worried about not having enough blocks.

>>8242143
That depends on how you want to encode things. There are 2^25 possible patterns of dots on your 5x5 grid, but ideally you want your system to work in such a way that most possible dot patterns I could enter are not valid passwords. Which means that some of the dots are used to encode a specific set of solved dungeons (or whatever data you want to store in the password), and other dots are used to verify that it's a valid password. Different encodings yield different numbers of possible passwords, different confidence that players can't guess passwords, and different complexity of generating / decoding passwords. (Please PLEASE don't make a huge list -- design a general system that can generate and verify the passwords for you. I could give you some hints on this topic, if you like.)

>>8230609
Why is the human body so fucking complacent about absorbing minerals?

>>8242123
No need to generate passwords manually; just use a hash that maps a number between 0 and 255 to a random-ish password.

You can save having to store 256 passwords by using a simple cipher. E.g.

a,b,k,q = 29832437821, 72187109983, 208827064559, 109967443571
def fwd(x): return (a*x+b)%k
def inv(y): return ((y-b)*q)%k
def tostr(x): return "".join(chr(65+(x/(26**i)%26)) for i in xrange(8))
def fromstr(p): return sum((ord(c)-65)*(26**i) for i,c in enumerate(p))

tostr(fwd(x)) converts a number between 0 and 255 to an 8-character password. inv(fromstr(p)) does the reverse.

a,b,k are random-ish primes less than 26**8. q is the reciprocal of a modulo k, i.e. a*q%k==1.

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>>8242167
>Please PLEASE don't make a huge list

Yep. That's me. I know it's amateurish and I've done a lot of that sorta thing already.

To give me credit. I do see how I could rewrite most of this in the pic by just making a function and having most of the individual variables share the same variable. (since they already share the same values)

>>8242185

I'm totally all for generating passwords automatically, but I don't understand what you've written in your example. I'm using Python 3 for scripting on this engine. are these functions native to Python 3?

>modulo

people have suggested this to me a few times and I've looked it up, but I don't understand that either.

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I found this weird rock today.
Why does it have a core like this?

>>8242203
>To give me credit. I do see how I could rewrite most of this in the pic by just making a function and having most of the individual variables share the same variable. (since they already share the same values)
What you need here is an array of checkbox objects (or pixel objects, or whatever those ob18 objects are).

>I'm totally all for generating passwords automatically,
Here's an example of a way to do it. Not related to >>8242185.

Take your 8 dungeon-cleared bits, and convert them to a number between 0 and 256 (this gives you an 8-bit number). Multiply by a 17-bit number; let's say 97379, which is prime (which means its bits don't have a predictable pattern). The result is a 25-bit number. Convert back to 25 booleans; that's your 5x5 password grid.
When interpreting a potential password, interpret your 5x5 password grid as a 25-bit number again, and check whether it's a multiple of 97379. If not, it's an invalid password. If so, divide it by 97379, and get your 8 dungeon bits back out.

It's just a simple example of a scheme, and it admits lots of variations, but it's already much better than making a large list of passwords. What are you gonna do if you add 3 more dungeons? Are you going to write 2047 passwords by hand? That way lies madness.

How do I reduce [math]\begin{bmatrix} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1\end{bmatrix}[/math]?

>>8242275
It is actually reduced.

>>8242275
[math]I[/math]

>>8242311
This is what I wanted, thanks.

>>8242307
we need to go further

>>8230609
Does a point have 0 dimensions?

>>8242318
A point is a location on a plane of n-dimensions. (1,2) would be a 2d point, (1,2,3) would be 3d, and so on.

>>8230609

Why is anything why come¡

>>8242318
Yes.

>>8242332
> (1,2) would be a 2d point
It would be a point IN 2 dimensions. The point itself is 0-dimensional.

A mapping R^m->R^n is an m-dimensional structure, not n-dimensional. E.g. a line is 1-dimensional regardless of the dimensionality of the space in which it's embedded.

>>8242123
Just generate K random passwords, ensure they are all unique, then distribute those to all the levels.
Even better is if you write something that will generate them in the exact format you want, too.

>>8242585

What's a K random password?

Is there a zero for the polynomial [math]x^3+2x^2+3x+2[/math]?

my worksheet answer is apparently -1 but i dont get the answer 0, i get -4

>>8230609
A={u,v}

B={{u},{v}}

Is A≠B correct and is A not a subset of B?

>>8230609
Find a power series representation of

[eqn]\frace{e^t-1}{t}[/eqn]

>>8242712
[eqn] \frac{e^t-1}{t}[/eqn]

>>8242699
if you substitute x by -1 you get
-1+2-3+2=0

>>8242699
No real roots, theyre all imaginary

>>8242024
Well, if I assumed correctly. A is a normalisation constant, i.e. some constant that makes the wavefunction squared = 1 when integrating from negative infinity to positive infinity.

>>8232016
>I have a penis that is 100 inches long. If you give me a couple billion dollars I could prove it to you with photos and a cheap video

Is there a zero for the polynomial [math]x^3+2x^2+3x+2[/math]?

my worksheet answer is apparently -1 but i dont get the answer 0, i get -4

>>8230609
will my potato farmers ever reach ultimate mcdonald status e-i-e-i-o

pls tell me O Gret Sci Oracul

>>8241170
>You just posted your answer. A ducted fan. the duct prevents a lot of the efficiency loss meaning the fan is still useful at smaller swept areas.
What if you want to increase thrust beyond even a single ducted fan? I know you can increase pressure by adding additional stages but from what I understand that is more useful for increasing top speed by increasing the velocity air exits rather than adding more thrust at low speed. RPM is limited by the blades breaking the sound barrier.

Would replacing one larger ducted fan with a group of smaller ones spinning at higher RPM generate more or less thrust?

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I'm learning physics and maths as a hobby like many other anons and am watching Walter Lewins lectures on electricity and magnetism.

The picture comes from the beginning of his lecture on rainbows. A minute later he will postulate that the angle δ is equal to 180° + 2*i - 4 * r ( with i and r corresponding to the angles in the picture ).

He tells his students to check it, but I can't come up with the reason it is what it is. Can some kind anon explain the identity to me, please?

>>8240523
You really should stop making fun of autistic people anon

>>8242744
There are three zeros because it is a 3rd order polynomial

>>8242709
anyone?

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How did he reach this result? I substituted x1 in the equation but I just don't get what he did

>>8230671
I'm a lurker, not a scientist, but I am allergic to nickel so I experience the same thing you do. It's actually a form of eczema. If it's only when you touch, it's a form of contact dermatitis, but if it's recurring out of nowhere, particularly during certain times of year, it's dishydrotic eczema. Both of these things can be treated with hydrocortizone or a prescription steroid creme.

>>8242885
Plug in 4py for x^2 in the RHS of (10)

You get y^2+2py+p^2 under the radical, which is (y+p)^2

>>8242744
-1 is a root.

2(-1)^2=2

Parenthesize your -1's correctly.

>>8242712
Just take the power series for e^t, subtract 1, then divide by t.

>>8242709
A and B are disjoint sets.

I'm not against religion or anything, but I have one of those religious friends who argues for the existence of God based solely on the fact that one cannot "disprove" his existence. I've explained to her that you also can't "disprove" something that doesn't exist. She also doesn't grasp why the burden of proof is on her for claiming something exists. Any advice on how to get through to her? I don't need to "convert" her, I just want her to realize that she isn't making a valid case for herself.

>>8242936
Use her logic on unicorns, Russel's teapot, aliens, or something to show her why it's inane to put the burden of proof on negative claims.

>>8242844
I assume the center line is supposed to be parallel to the top line (I didn't watch the video).
Let O be the center of the water drop, and D the point where the line from C intersects the center line. Let X be a point on the center line where on the left side (where the hand is).

(clockwise)
∠XOA = i
∠AOB = 180° - 2r
∠BOC = 180° - 2r
∠XOC = i + 2*(180° - 2r) = i + 360° - 4r = i - 4r
∠COX = 360° - (i - 4r) = 4r - i
∠DOC = 180° - ∠COX = 180° - i + 4r
φ = 180° - (i + ∠DOC)
δ = 180° - φ = 180° - (180° - i + ∠DOC) = i - ∠DOC = i - (180° - i + 4r) = -180° +2i - 4r

So if you find out what did I fuck up you'll have your answer, I guess.

>>8243042
Thanks, man! I think you have the sign of XOC backwards, this is how I think it should be fixed:

XOC = 360 - ( i + 180 - 2r + 180 - 2r ) = 360 - ( i + 360 - 4r ) = -i + 4r

DOC = 180 - ( -i + 4r ) = 180 + i - 4r

φ = 180 - ( 180 + i - 4r + i ) = 180 - ( 180 + 2i - 4r ) = -2i + 4r

δ = 180 - ( -2i + 4r ) = 180 + 2i - 4r

>>8242699
It's cubic. How can it not have a (real) zero?

Any polynomial of odd degree tends to opposite infinities, so must cross the y axis at some point.

>>8242936
> argues for the existence of God based solely on the fact that one cannot "disprove" his existence.
The entire point of pastafarianism is to address that "argument".

Also try to explain why this is "not even wrong".

What are the differences between these:

Directional derivative
Covariant derivative
Contravariant derivative
Connection
Affine connection
Exterior derivative
1-form
Lie derivative

I can understand their definitions but can anyone produce some neat way to structure them?

How do they relate to one another? Which ones are special cases of the other ones? Wich ones are equivalent?
How can i express these in terms of each other?
Can anyone give any examples to illustrate their differences?

Partial answers appreciated also

>>8234602
x=1/(1/x) is not a substitution, its just moving it around a bit. You can think of it as dividing the whole equation by (x * 1/x) (dividing by 1 doesn't change anything). The x (or n) in the front gets cancelled out by dividing by x, and the 1/x is left in the denominator.

x=n by the way, i hope it got clearer

>>8240537
what about it it?
it has the same size as the natural/rational numbers.

>>8243289
yes

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Okay, so I'm trying to self teach physik, and I'm doing the very first lecture on Khan academy r n (hate all you want), and I'm already confused, partly because my main language isn't English.

Anyway, vectors and scalars. What exactly are they? I just know so far what they represent.

A vector has a magnitude as well as a direction, unlike a scalar, which only has a magnitude.

In case of motion, is distance a magnitude? Distance represents the size/amount of something?

Could you please name a couple more examples of vectors and scalars? (ex. like distance is a scalar, what is current though?)

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If language didn't exist, but math still did, would it be effectively employable as language?

Would it just evolve into something that resembles human languages today anyway?

Don't meta-mathematical and meta-linguistic descriptions of each field boil down to pretty similar principles?

>>8230762
>could

Try harder, kike.

>>8243363
Giving an answer is pretty hard the problem is that alot of things are both talked about as scalars and as vectors.

The distinction is weither direction matters.

There are things that are completely independent of direction.
Take area as an example it obviously doesn't have a direction so it has to be a skalar.
Same goes for distance. No matter from which direction you measure a distance it will always be same.

Other examples are density, charge, weight, duration, amount,...


Whats left are things that should have a direction.

Speed is an example for such a property. If you are talking about a speed you are talking about something that should be a vector because direction matters if you are going from point a to point b or from point a to point c.
Most things that are vectors are either force or speed.

>>8243363
Charge and mass are examples of scalars.

Any vector quantity has an associated scalar quantity, which is the magnitude of the vector.

Velocity is a vector quantity; the magnitude of which is the scalar quantity called speed.

Displacement is a vector quantity, the magnitude of which is the scalar quantity called distance.

For many quantities, the same name is used for both the vector and its magnitude, e.g. force and acceleration can be either a vector or a scalar.

Vectors may be represented either in Cartesian coordinates (X/Y/Z components) or polar coordinates (magnitude and direction).

>>8242942
Get this, she believes unicorns and dragons are real, but extinct. She also believes she's a faerie, but I usually don't bring that up just to give her a little bit of credit. It just baffles me how someone can just disregard reality the way she does.

>>8235020
s1 elimination - Br2/CCl4 -> NaNH2/lq NH3 i guess ?
s2 antimarkovnikoff hydroboration or sth like that
s3 i dont know wtf that is supposed to be honestly

>>8243642
I strongly suspect that anything resembling rational argument would be pointless here.

>>8243729
You misspelled my name.

>>8243758
Unfortunately, I believe you may be right but, like her, I have trouble accepting this. She really is an intelligent person otherwise, but when it comes to matters of faith and fantasy, this sort of thing happens. And it's not like she shuts me out, we debate back and forth all the time and she concedes when I present infallible logic. So I think I've broken through, but the next time it comes up, we're back to square one. Like there's a reset button in there. It genuinely makes me sad and I don't know what to do.

>>8243454
>>8243558
Thanks mates. Helped me out!

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I'm kind of self teaching and I was wondering, why am I immediately able to write the Pithagorean theorem as [math]|z|=\sqrt{x^2+y^2}[/math] if [math]x[/math] and [math]y[/math] need to be calculated first? I can't really word this in a way I'd like to... another go, why can [math]x[/math] and [math]y[/math] be considered the x coordinate of A and the y coordinate of B?

>>8243945
The complex numbers are really just an algebraic structure on R^2. In other words, the complex number a + bi is really the ordered pair (a,b), with specific rules for arithmetic. Namely,

[math](a,b) + (c,d) = (a + c, b+d)[/math]
[math](a,b) \cdot (c,d) = (ac - bd, ad + bc)[/math]

So really |z| is just the standard euclidean norm, the same one from R^n.

Also, Pythagorean, not Pithagorean.

Any good resources to teach myself Architecture and Architectural Drawing?

Thanks.

I'm trying to actually learn math from the beginning, started following the Serge Lang - basics mathematics and so far so good, but i got stuck in this exercise:

1. Express each of the following expressions in the form 2^m.3^n.a^r.b^s, where m,n, r, s are positive integers.

for example:
a) 8a^2.b^3.(27a^4).(2^5ab) = 2^8.3^3.a^7.b^4

the one i'm stuck is this one:

b)16b^3.a^2.(6ab^4).(ab)^3

So far I got: 2^4.3^x.a^9.b^10, but I can not see what to do with that 6 to get the value to fill the "3^x"..

excuse my dumbness, ty

>>8244277
6 = 2 x 3

>>8242242
I also would like to know what the fuck this is

>>8242242
I don't know much, but that might be a fossil? It looks like a seed in the center.

>>8243423
What would a species without language capabilities do in response to being presented with math? Would they even recognize any meaning in the characters or syntax? I don't think so.

Numbers without context aren't particularly useful. A species/community that doesn't develop some agreed set of labels isn't going to assign or derive such context.

So basically you'd have one lonely clever creature appearing to do nothing/something useless while the others with no concept or potential to form one of what is happening totally ignore/disregard these actions.

Your questions either answer themselves or are incoherent.

Asking if you could use a form of expressing logic as a language without language is like asking if an animal could use an explosive reaction as a weapon of war without knowing if or why it triggered the explosion. The answer is no. If the concepts are not in use, they are not in use.

>>8244288
although thats pretty obvious I didn't look it that way because the exercises seems to state that all elements should have an exponentiation, but that seems like the only answer

so, if I'm not wrong
16b^3.a^2.(6ab^4).(ab)^3
should be
2^4.3.a^9.b^10
thanks anyway

If we grounded a copper wire in the urf and then dragged it 1,000 miles into space...would the end of the wire have the same gravitational pull as the earth?

>>8242646
k is an arbitrarily chosen variable, i assume

File: 146623243959.jpg (5KB, 374x347px) Image search: [Google]

5KB, 374x347px

>digital images and videos are encoded using a fourier transform

It's clever and it makes sense.
But how the heck did they come up with this?

Did they just try different mathematical ideas and stumbled on this?
Was there some really smart guy behind it all that came up with the idea out of the blue?
How do you go from "this will simplify heat equations" to "I can use this to watch anime"

File: Capture.png (142KB, 1052x616px) Image search: [Google]

142KB, 1052x616px

I have no clue what to do here.

>>8244378
They came up with it because it makes sense..
Videos don't have many pixel-by-pixel details, but there's plenty of things that could be expressed as gradients, which fourier transforms were perfect for.

>>8244378
DFT has been around since the 60's and maybe before, so it was on the minds of digital signal processors long before jpeg.

But the most important idea behind the use of Fourier transform is that the human eye is less sensitive to high frequency changes than low, allowing the higher frequencies of an image to be down-sampled and usually zeroed out. This, followed by a clever serialization strategy, results in a data stream with large groupings of zeroes, which makes it quite amenable to Huffman encoding.

That is my understanding of it anyway.

>>8230779
Space is very cold, yes, but spaceships are insulated. Thermal resistance is very similar to other sorts of resistance, like electrical. Space may have near zero thermal resistance, but the spaceship has high thermal resistance to make up for that, slowing the rate of heat dissipation (the analog being current).

Our planet spins @ X speed
(Daily rotation)

Each planet in our solar system rotates around the Sun
(Planetary year cycle)

Our solar system rotates around the center of our galaxy
(Whatever it's moving)

The Milky Way galaxy is flying through space
(Again it's moving)

So as we hurdle through space like a speeding locomotive.

My question is....What would happen if you stopped?
Or possibly if it's feasible to answer such a question...What would it take to stop in relation to all that is around you?

>>8244501

I don't know, but I don't think it is feasible

It's all relative.
The concept of "movement" is only really defined by distance changing between two objects.

I actually have a similar question.
In time travel discussions, there is always one smart-ass saying "well, if you traveled back in time even one second, you would be in the middle of space because earth and the solar system and the galaxy are all moving very fast"

And I suspect that that is a naive thing to say, since its all relative, and you are only moving very fast in relation to some imaginary center of the universe

>>8244447
nvm

>>8244501
> What would it take to stop in relation to all that is around you?
> all
then everything would stop moving...until it started moving again from unbalanced forces.

What I think you're asking is (correct me if I'm wrong) "What would happen if we stopped with respect to a universal reference frame?"
The answer is, a universal reference frame doesn't exist

>>8244660
No I mean like pick an arbitrary point in space and stop.
The universe continues expanding, the galaxy continues careening through space.
The reference frame continues to exist.
From an observers point of view on Earth, the person or ship that stopped appears to accelerate FTL.
From the observers point of view from the stopped ship, Earth has now accelerated FTL

Will it be hard to get into bionics R&D with a CS degree? I'm halfway through and starting to think about what to do my Master's in

>>8244520
If you just use time as a fourth coordinate there's nothing wrong with that.

The "smartass" is just assuming that the person building a time machine or whatever is only changing the time coordinate and not compensating for the movement of the earth.

Correct me if I'm wrong, but wouldn't using time travel in this method to leave behind a trail of some sort of beacon provide us with a very good insight into how things move in the universe (with diminishing returns)?

Since everything is moving to some extent.

>>8231164
>I watched YT vids of a professor solve and explain HS math

I'm interested, can you tell me the name?

>>8235020
http://docdro.id/jdZy5MU

there you go.. the rest of work - for your own sake - should be done by yourself

>>8234468
Then it isn't a theorem anymore.

>>8245270
Unfortunately he's a local professor, doesn't hold lectures in English. Now unless you speak Croatian though...

Underneath the 3 Laws of Robotics, can a robot ask a human to order it to destroy itself?

The third law loophole allows a human to order a robot to self-terminate but does it also violate the rule if the robot , through their own choosing, ask for it?

>>8245806
> Underneath the 3 Laws of Robotics,
>>>/lit/
Totally not science.

Why do electronics use DC? Isn't AC superior in every way?

>>8246506
0/10

>>8246524
>DC pleb detected
Learn to make your circuits work both ways like real men.