/sqt/ - Stupid Questions Thread

>>8716741

>>8722845
>OPs who ignore thread meta and don't have the string that people usually search for when trying to find the thread
In my experience, it's always a good idea to have a properly made thread even if an improperly made one exists.
The improperly made one flounders because half the people assume one doesn't exist, but if a properly made thread exists it can gradually take over.

Cross-linking the threads interferes with this process though; the improperly made thread receives all the attention of a normal thread by leeching off of the improperly made thread, causing the properly made thread to die, resulting in a failing improperly made thread again.

How can we taste food if the atoms are technically not touching?

>>8722900
>In my experience, it's always a good idea to have a properly made thread even if an improperly made one exists.
what's wrong with the other one?

>>8722928
Most people search "SQT" when looking for these threads.

>>8722909
Chemical reactions or something

>>8722836
With all the focus on curing cancer ... why not focus on the #1 noncommunicable cause of death world wide...

>>8722909
Define touching

>>8722836
>With all the focus on curing cancer
On treating the symptoms: because this is $$$.
How would people learn if they didn't suffer?

If you spin clockwise on a chair for one minute and you get dizzy, will spinning counter clockwise for one minute undizzy you?

>>8722909
Groups of atoms bind with receptors on the surface of the cell, releasing intracellular signaling molecules. For sour and salty, it's thought that H+ and Na+ ions passing though ion channels depolarize the cell directly. I don't have a very good understanding of any of these pathways though

>>8723149
yes

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How can I calculate the velocity of a projectile in a catapult? What data do I need and how can I do it?

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>>8722909
Atoms still have unique properties. Protons and neutrons may never actually collide but electrons can freely interact with other atoms and can even be shared amongst atoms. Within a molecule, electrons are not shared evenly, polarity is not uniform, and localized poles are created as a result, this can even affect the structure and reactivity of the molecule. Receptor binding usually doesn't involve direct bonding through sharing electrons, instead they fit together with a specific grouping of atoms out of a molecule and corresponding poles on the receptor will hold them there. Binding with the target molecule will cause the receptor to undergo structural and functional changes, which can do any number of things inside the cell

>>8723149
No, your inner ear gets overstimmed freaks out. More stim won't help. Also some people say it's because you've spun up the fluid in your ear, so inertia keeps it going for a while. I, however, find in hard to believe that a few mLs of fluid in a fuzzy tube has trouble keeping up with the tube.

[math] sin(cos^{-1}(x)) = \sqrt_{1-x^{2}} [/math]

Does this bring us any closer to defining sine or arccosine as a regular function?

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>>8722836
Any topologist here who could toss a bone to a retarded sophomore? This is specifically about the "usual" topology of real numbers.

For pic related, I am trying to prove that the 3 definitions of compactness are equivalent. Specifically I am trying to prove that:

Every open cover of a set K has a finite subcover that also contains K
is equivalent to:
K is closed and bounded

At the beginning where it says assume K satisfies (i) and (ii) it means that you have to assume that K is closed and bounded, and that every sequence in K has a subsequence that converges to a number in K

The problem outlines a proof strategy you are supposed to follow but I am getting fucked in the ass by part a)

Why is it? I am sure I am missing someting big about open covers.

I just need a hint for a) and I am sure that then I can do part b)

So far I have been able to prove c) and d) (assuming a) and b). obviously)

c) follows from the nested interval property of the real numbers

d) The follows from the fact that if an open set contains a number, then it contains an epsilon-neighbourhood around that number. Then I can pick n0 so big such that the length of In0 is even smaller than epsilon and then In0 will be contained in that epsilon-neighbourhood, which is then contained in the open set. Therefore In0 is contained in a finite subcover, but also In0 is NOT contained in a finite subover (part b) ) which yields a contradiction and then QED.

So please help with part a). I need hero. I need a hero at the end of the night.

>>8724190
if A1 intersect K and B1 intersect K both have finite subcovers then you can build a finite subcover of I_0 by combining these two subcovers. but then this would also cover K, contradicting having no finite subcover

>>8724230
whoops:
if A1 intersect K and B1 intersect K both have finite subcovers then you can build a finite subcover of K by combining these two subcovers. (contradicting having no finite subcover)

>>8724234
Yeah, I get that. But what if only one of them has a finite subcover?

From what you said only, I cannot construct the sequence of intervals asked for in B).

For example, imagine that I0 is the smallest closed interval that can contain K. Then I bisect that and I get two "equal" parts of K.

Why couldn't I have a finite subcover of one part only?

>>8724251
>>8724234

Wait nevermind. You are a fucking genius.

You are right, both can't have finite subcovers, so at least one must need an infinite amount of open sets to cover it. And then I pick that one for my I1

then I repeat that process to get my sequence of In

FUUUUUCK.

Man you are so right and last night I was thinking about that but I got caught up in the details I mentioned in >>8724251 and missed the forest for the tree.

Am I going to make it? Will I ever get rid of this brainletness? Anyways, thank you my man for showing me the forest.

>>8722836
How can we know the number of protons in an ion's nucleus without looking at the nucleus?

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If you're shaking a spring back and forth to create a certain harmonic, with the other end fixed, is it an open or closed harmonic? It looks like it's closed, but if you're moving the end back and forth, is it sort of half-open?

>>8722836
Because normies can't understand scientific jargon. Any scientist doing cancer research is focusing on this, but in order to get funding they have to use emotional appeals and kindergarden language.

>>8723241
You will need the angle of inclination, and the horizontal or maximum vertical displacement. gravitational acceleration can be assumed to be -9.81 ms^-2.

>>8724341
Closed at one end

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>>8722836
Why does taking off my helmet kill me?

Couldn't I just hold my breath in space assuming my body or suit isn't damaged?

>>8725645
>does taking off my helmet kill me?

it would be very painful

>>8725645
space is fuckin cold man

>>8722836
Can I get a job with a pass/credit average and a great thesis and project? My uni weights a fail in such a way that it takes 2 high distinctions for it to average to a pass.

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>>8725645
Coldness, pressure levels, radiation, you name it

How am I supposed to solve the problem in my pic? I've tried it with one and two images, both placed on the x-axis, but the calculations didn't give me the distance from the origin, or the charge.

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>>8726055
Nevermind, I got this!

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I'm supposed to find the IUPAC for that structural formula.

I got thrown off by the (CH2)4 so I thought trying to draw it out might help. Before I attempt to name it, is the line structure even correct? Should I even need to visualise the structure to be able to given an IUPAC for that structural formula?

>>8726113
Nvm, I did draw it wrong it's 3-ethylheptane. Sorry I can't delete that potato photo post

What are some of the best chemistry books? Intro to complex Chem.

>>8722836
sauce tho?

Remind me how do you calculate this infinite series?

1 + 1/2 - 1/3 + 1/4 - 1/5 + …

How long does it take your university to release exam results?
I took an exam in automata theory, and it took 3 weeks to get my results, but I think it's acceptable due to the nature of the exam (no cookie-cutter answers, the TA/professor/whoever has to check everything by hand).
Meanwhile i also had a multiple choice test in economy, and i'm still waiting for results a month later, even though it should be fairly quick to evalulate.
>>8722928
>>8723028
>Most people search "SQT" when looking for these threads.
Yeah, that's how i found this one. Didn't even notice the other one exists

>>8726469
-1+1/2-1/3+... = -ln(2)
1+1/2-1/3+... = 2-ln(2)

>>8726469
>Remind me how do you calculate this infinite series?
> 1 + 1/2 - 1/3 + 1/4 - 1/5 + …
-ln(1-x)=x+x^2/2+x^3/3+...
Substitute x=-1 and compare both series, you can see that yours is 2-ln(2).

>>8724276

Mass and charge measurements

I've got this problem:

1-sin^2(θ)=0.5

And I've got to find theta where -90<θ<90. Can anyone help? I think the answer is -45, 45 but I'm not sure because symbolab gives some 5pi/4 mumbo jumbo.

A little bit of complex variables:

How would I find a formula for integral over a region gamma f(az+b)dz where a,b \in (complex) and a =\ 0?

I can see it requires a change of variables but am confused how to go about it.

>>8726576
45, -45 you're referring to degrees. 5pi/4 would be in radians (the conversion is x*pi / 180 ).

After you convert it to radians you have to make sure it corresponds to the correct quadrant with respect to the unit circle.

>>8726576
Yes, +-pi/4 is correct.

>>8726576
>>8726591

Also, forgot to mention by x I am referring to the number of degrees you want to convert.

>>8726591
>>8726595
>>8726596

So 45 is OK if I want it in degrees? They only want it between -90 degrees and 90 degrees. I have to look up quadrants.

>>8726604
>1-sin^2(θ)=0.5
Yes it should be -45 and 45 (-pi/4 and pi/4)

>>8726654

Thanks. My powers of observation are fucking terrible, not noticing it was radians is more shameful than just not knowinghow to do it. Thanks.

>>8726604
All I meant by the quadrants is essentially that:

by them asking for between -90 to 90 degrees they are essentially asking for the solutions on the first and fourth quadrants.

Don't lose sleep over it though.

>>8726661

Oh I get it, the quadrants of a circle. Thanks.

I have a question.

Given that -90 degrees < x < 90, what is sin(60+x) = cos(x)? It also asks to use the addition formulea.

Suppose A, B and C are three sets and Cl(X) denotes the closure of X

Does Cl(A) = Cl(B) U Cl(C) imply A = B U C ?

>>8727087
no, just play around with some intervals and you'll get easy counterexamples

Is it possible to grow seeds on a cup full of cum?
I mean, semen has water and nutrients.

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>>8727116
you can at least grow mushrooms

>>8727116

Two problems. First you would have to keep it fresh and full. Second, most of the nutrients are in proteins the plant can't break down.

So imagine you roll a 10 sided die and flip a coin. If the die doesn't come up 10, and the coin comes up heads, the die is rerolled and the coin reflipped. This increases the probability of resolving on a 10 to 55% via the equation A + B - AB = C.

My question, is this actually used for anything in real life? This is suppose to describe the chance of a temporal computer successfully extracting a solution from noise.

>>8727097
Fuuuck.

I wanted to use that to prove that if a set is connected, then the closure of that set is connected.

I have an easy proof for the real line, as all connected sets are intervals but I thought this proof was cheap and was really ignoring the nature of connected sets. So I want to use a proof that does not use that fact, so that the proof holds up for higher dimensions and such.

Any hints my man?

>>8727126
>Implying the plant doesn't have proteases

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3014533/
10 second google session.
People sure talk alot of bullshit on this board.

Is there any fuckery you can do with topology to make a tiled plane composed of regular polygons with over six sides? Like taking a hex grid and turning it into a hepta grid.

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Fuckin' magnets, how do they work?

>>8722836
How prey tell, would you stop cells from detaching and moving around the body? Besides exising them from the tissue.

>>8727138
I'd say you can use the property :
X is connected iff
All continuous functions from X to {0,1} are constant, where {0,1} is the two-point space endowed with the discrete topology.

>>8727202
I don't "know" that property, as in I have not seen it. I am working through an introductory analysis textbook that touches on the topology of real numbers. All I "know" is the basic definition based on sequences

>>8727215
What exactly is your definition of a connected set ?

>>8723871
No, the trig functions cancel
Just express them as infinite sums like the rest of us

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>>8727230
Pic related.

From Theorem 3.4.7 follows a really elementary proof but I want to use only the definition and the previous theorem.

>>8727241
Ok so you are only working on subsets of R ?

Proving your stuff without proving first that your connected set is an interval, seems very tedious, because the closure could be anything, so it's difficult to work with it. Also proving a connected set is an interval is not that hard.

>>8727263
>Proving your stuff without proving first that your connected set is an interval, seems very tedious, because the closure could be anything

Yeah, I think so. Maybe this book intended for the reader to go with the easy proof.

>Also proving a connected set is an interval is not that hard.

Yeah, that's theorem 3.4.7

>>8727265
I mean proving it from theorem 3.4.6, or even from the initial definition.

can anyone help me with binary logarithm? can't figure it out, can't find any good resource either.

lets say logbase2 of 1.6 and logbase2 of 0.6.

so its [math] 2^x = 1.6 [/math] and [math] 2^x = 0.6 [/math]

how do I figure the 'X' value?

How do you guys label potential and kinetic energy?
PE and KE?
U and K?
V and T?
something else?

>>8727446
U and K
And fuck outta here with R, I'm a subscript man

I got my exam back today and recieved a 70

I missed this question which I'll ask my teacher on how to do it.

The answer online I find is -1

The original question is

-1(Sec(pi/12))
——————
csc(5pi/12)

I first did converted to
1/cos
———
1/sin

Then tried flip them and use the complementary angle theroem.

I still got it completely wrong. Like way off base.

I noticed online that 5pi/12 can be converted to (pi/6)+(pi/4)

So that gives me

-1(1/cos(pi/12)) ° (2+ sqrt(2))


The question asks to use the fundamental identies and or complementary angle theroem.

What did I do wrong and how could I have fixed it?

Thanks

Does anybody know how the strength of anesthetics is measured? Like how strong is 0.4% tricaine compared to whatever dosage of morphine hospitals will give to people?

>>8725645
the main thing that gets you is the difference in pressure between the inside of your body and the outside.
this being said you can presumably survive a little bit of exo, maybe 20 seconds but that's a complete guess.

I am 22 and have been leading a lackadaisical, whimsical lifestyle since leaving high school. I recently visited my mother and ended up finding a few binders of schoolwork only to find that I had a little bit of trouble recalling how to solve some of the math, and had no recollection of the answers to some of the history and literary problems.

What does /sci/ do in its spare time to keep the mind sharp? (Aside from post on 4chan.) I intend on going to a college at some point in time, but I admittedly got a little discouraged when looking at papers that were 5 years old. Idle hands and all that jazz, I suppose.

FYI: I have no inclination to be a polymath, but I wouldn't mind being well-read and knowledgeable concerning a broader sphere of subjects--typically found on a campus. Maybe half-a-mile wide and 2 feet deep, you know? Oh, and don't ask the hard questions (what do you want to be? where do you see yourself in 5 years?) because, as my father'd tell me, I still have no good answers for those questions.

>>8722836
Holy shit nobody's ever thought of this before

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>>8722836
???

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>>8727787
Maybe it was a composite of multiple photos, taken at different times, and spliced together. Or it could just be a shop, do you have the sauce

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>>8727805
http://visibleearth.nasa.gov/view.php?id=57723
Yeah but I get what you're saying, I can't believe I didn't think of that.

>>8722836
All cancer treatments can attack metastasis. Metastasis are just the same cancer cells, but in a different place. It just so happens that at that point, most treatments aren't enough to help most patients.

Also, the body does recognize and attacks cancer cells, but they reproduce so fast the body can't get rid of it.

Also, quemotherapy basically attacks cancer cells (as well as many others). They work by being in the blood and when they pass through the tumor they are absorbed by the cancer cells.

Stupid statistics question:

For some estimate of mu (mu-hat) described as a function of 2 independent variable, how do you compute mu-hat so that one may determine the bias, variance, etc.

Eg.

mu-hat = (X[1] + 2X[3]) / 3

>>8722836
>and it sounds like it would be much more straightforward

What you're talking about is angiogenesis, the formation of new blood vessels from pre-existing ones. It's not simple. Like with any other macroscopic process, it has like a hundred molecular factors involved. And most of them overlap. And they have redundancies built in. And double redundancies. Imagine the most powerful firewall or whatever computer jargon you nerds use. Try cracking that.

>>8727436

2 = 1.6

Is the same as: log_2 1.6 = x

All we are looking at is what power we need to raise 2 to to get to 1.6. If your calculator has a log button that allows you to enter the base and the characteristic, you can plug it in an get x = 0.6780719051.

You calculator may only have a "log" button, in which case you need to change to base 10 first. Whenever you see "log" on its own with no base its always base 10 or e, in this case, 10. To do that, you change it from:

log_2 1.6 = x to log1.6/ log2 = 0.6780719051, same answer as we got before.

Likewise, log_2 0.6 = log0.6/log = -0.7369655942

Basic log rules are:

log_a a = 1
log_a 1 = 0
log_a (1/a) = -1
log_a m + log_a n = log_a mn
log_a m - log_a n = log_a (m/n)
log_a x^n = nlog_a x

I live in California. Should I be worried about sushi in the wake of Fukushima?

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Can someone PLEASE show me actual math behind this as opposed to y is sin x is cos viola equation is 2y-3x=2

>>8728891
how were you introduced to polar co-ordinates?

this problem is just showing that not everything is already in a nice form for you

>>8728891
[math]\sin{\theta}=\frac{opp}{hyp}=\frac{y}{x^2+y^2}[/math], also [math]\cos{\theta}=\frac{adj}{hyp}=\frac{x}{x^2+y^2}[/math], finally [math]r=x^2+y^2[/math].

substitute those in and cancel out [math]x^2+y^2[/math] to get c.

>>8729291
sorry i missed the square roots around all my [math]x^2+y^2[/math], pythagoras theorem

someone please explain what [math] \mathbb{R} / \mathbb{Q} = \{ x+ \mathbb{Q} \mid x \in \mathbb{R} \} [/math] is structurally

>>8729317
An uncountable, abelian group

>>8729317
did you make a mistake or do I just not understand your notation?

>>8729342
that looks like the reals factored by the rationals

if it is, then examples of elements are [0], [e], [pi]

>>8722836

If you shoot a gun into the air at a 85 degree+ angle, when the bullet comes back down can it kill somebody?

What's mathematical modeling? Is an equation like pv=nrt or f=ma a model?

Is EE the best engineering major for a math fag?

>>8722836
Because the real world works on making a buck and prevention is bad for existing business.

>>8729366

isn't it any {reals + some rationals}? not that your example is wrong but its more general this way. Pretty interesting to know what you CAN'T do with that set.

>>8725645

Shake a can of coke and open it. That's what's happening to your blood vessels when you're in a vacuum.

>>8727446

Just try to minimize sharing letters. If you're using v for velocity and t for time it's not a good idea to use V for potential and T for kinetic. Aside from that it doesn't matter, so long as you make it clear what they are at the beginning and stick to that convention throughout.

>>8731162
its equivalence classes of reals modulo rationals (i.e. you only care what the real number is 'up to' a rational number)

so you have equalities
[e]=[e+p/q] for any rational p/q

in particular the identity in this group is [0] which is the equivalence class consisting of all the actual rational numbers

>>8727754

Math: take a look at math olympiad problems, also project euler if you want to do math+programming.

Books: you could do worse than read all those "a very short introduction to ..." books -- they're a quick read and written by experts in the field. Many hard problems are interdisciplinary, and one of the worst failure modes is when people working on them don't know that other people in different fields are working on similar things, and might have already made decent progress using alternate methods. If you don't even know of prior efforts you can end up reinventing the wheel. Biology is particularly horrible for this: at one point a nutritionist came up with fucking Riemann sums because he'd never done calculus ( http://care.diabetesjournals.org/content/17/2/152 ). Just being aware of what other people are working on can save you a lot of trouble.

>>8726469
can we make this 1 + (sum) - (sum)

where is that "entry level books" png? pls thanks

>>8729534

yes

Is AI primarily a software or hardware problem?

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just to check, this means a quarter-circle with a radius of 9, correct?

>>8731475
radius 3 brainlet

which one of you autists is this?
http://mathoverflow.net/users/91341/robert-frost

>>8731482
> Everything moves at the speed of light, only its direction changes

This reminds me of something. Isn't that a legit interpretation ?

How do you convert weeks to months?
What's the expression?

>>8731475
Yes, it is a quarter circle.

What's your stance on googling homework questions?

For example, we had to find a way how to swap two cells on Random Access Machine without using registers. I found the answer within 30 seconds of googling. Same thing happened when we had to solve the egg drop puzzle (N eggs, K floors, find highest floor you can drop an egg without it breaking). I still had to understand the answer, so I could present it in my own words.

On one side, if I'll find the correct answer by myself, I'll learn much more about the problem.

On the other side, these problems aren't that important and the knowledge obtained by solving them won't help me in solving the other problems, aside from the general skill of solving problems.
It would definitely take some time before I would find the solutions by myself and I have a lot of other homeworks to do.

There's also some amount of knowledge obtained by knowing how to solve the problem, too, so it's not like I failed to learn anything. I believe the knowledge gained by finding the answer isn't worth the time, since most of the "reward" comes from knowing the answer.

What's your opinion, /sci/?

>>8731477
oh shit yeah im dumb
thanks

>>8728891
quick method for something like this, requires basically no understanding of polar equations :
try and plug in an angle of 0 in the polar equation to get the radius and you got yourself a coordinate, which is (-2/3,0), then, try to plug that in one of the equations and see which corresponds, c seems to get it right, and only c
it's very efficient for these kind of questions i guess, you already have the answer down

Why did plants colonize land? It should have been easier to continue to live in the water. How did they take the first step to live on land?

>>8731767
>It should have been easier to continue to live in the water
Easier, but with more competition. If you're first on land, no one can stop you without also having to adapt to land. It's a valid strategy.

>>8731643
>the knowledge obtained by solving them won't help me in solving the other problems, aside from the general skill of solving problems.

It depends, it will help you solving other problems of the same nature because solving the problem will require you to build a extensive model of the situation and understand many of aspects of it.

But yeah understanding the solution is already valuable work. If you don't intend to become the best in that topic, I guess it's good enough.

>>8731777
That's interesting, thanks. Would you happen to know how plants evolution worked? For example, during development, did roots, leaves and vascular tissue develop alongside eachother? Because Vascular tissue requires roots, and roots require vascular tissues.

>>8731533
Didn't think this was that difficult of a question.

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Hey guys I got a fun stupid question here.

I need a SiC(silicon carbide) heating element in the shape of pic related.
Who sells it here in the united states?
All I find is tubular shapes.

>>8732089
>>8731533
It's not exactly hard but it can have different answers depending on what you need it for

# weeks * (7 days/1 week) / (days per month) = # months

where if you want a rough estimate, you could use
days per month = 4
If you were just gonna convert it later you could use (and wanted a better approximation)
days per month = (365 days/1 year) *(1 year/ 12 months)
If you were only using certain months you could convert them one by one
days per month (january) = 31
days per month (march) = 31
etc etc

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I have been battling with pic related since yesterday and today, after at least 15 hours of no progress, this proof came to me while I was coming back home.

I thought I would not even be able to prove this theorem, so this proof to me is too good to be true so I want someone with a better eye to see if it is not shit, as it is not the first time a proof too good to be true of mine happened to be completely fucking wrong. For background, this proof is meant only for the real numbers.

It goes like this:

As [math] G_1 [/math] and [math] G_2 [/math] are open sets then that means that they are the arbitrary union of open intervals. And because they are dense that means that their intersection is nonempty.

Furthermore, their intersection is the intersection of two open sets, which means it is also open! But if it is an open set that means that this intersection is also made of the union of arbitrarily many open intervals.

Pick any of those open intervals and call it [math] (a,b) [/math]. Then pick any [math] x,y \in (a,b) [/math] such that [math] x < y [/math] and construct [math] [x,y] [/math] and for my argument, call it [math] I_1 [/math].

Note that [math] I_1 \subseteq G_1, I_1 \subseteq G_2 [/math] because it is a closed interval, inside an open interval that is inside of the intersection of [math] G_1 [/math] and [math] G_2 [/math].

For simplicity, also let [math] I_2 = I_1 [/math].

Then to construct inductively the next members of this family of sets, suppose [math] I_n = [c,d] [/math]. Consider the intersection [math] (c,d) \cap G_{n+1} [/math]

As [math] G_{n+1} [/math] is dense, this intersection is non empty. And as it is the intersection of two open sets, the result is an open set. Pick an arbitrary open interval from this resulting intersection and call it [math] (e,f) [/math]. Then pick some [math] g,h \in (e,f) [/math] such that [math] g < h [/math] and let [math] I_{n+1} = [g,h] [/math].

cont.

>>8732478

Note that [math] I_{n+1} \subseteq G_{n+1} [/math] and [math] I_{n+1} \subseteq I_{n} [/math] and

Now, the set of [math] I_{n} [/math] is a family of contained closed intervals, and by the nested interval property their infinite intersection is non empty.

Let [math]t[/math] be a member of this intersection. It has the property that it is inside all of the [math] I_{n} [/math]s. But each of those sets was contained in the correspondent [math] G_{n} [/math], which means that [math] t [/math] is also inside all of them!

Then, by definition the infinite intersection, the [math] G_n [/math] contains at least [math]t[/math], and thus is non empty.

Little career related question here, hope you don't mind.

If you work really hard to study maths on your own, can you hope to do a PhD in maths with a master in Optics and Nanotechnologies (so, basically experimental physics) and an engineering diploma in Materials Engineering ?

I like what I do in engineering, plus it's a nice thing to have on your resume, but what I'd like to do is a phd and become a researcher either in theoretical physics or in pure mathematics.
My school is not too bad, but not the best of the field either. I also kinda messed undergrad, leaving me with a GPA of about 2.8 (my country doesn't use that scale so I used a converter).

Anyone majoring in either pure maths or theoretical physics, or anyone else willing to give a bit of info, I'd be really glad. Thanks.

>>8732503
>If you work really hard to study maths on your own, can you hope to do a PhD in maths with a master in Optics and Nanotechnologies (so, basically experimental physics) and an engineering diploma in Materials Engineering ?

Only if the PhD is in applied mathematics, as then your doctoral thesis could be something related with your other disciplines.

If it is in pure mathematics then you either have to be crazy, or you have to want to never get out of school because there is no way you can start a PhD in mathematics with a background in engineering (which is all you will have, given your choice of masters). You will have to take like 9 years in your PhD because lets say that you are smart and can learn all of undergrad mathematics in 2 years, then you can probably spend 7 years actually working in graduate level mathematics and then finishing your thesis.

Basically, fucking crazy.

>what I'd like to do is a phd and become a researcher either in theoretical physics or in pure mathematics.

Oh...

When we forget a memory, where does it go?

>>8732523
Alright, thanks for the hard truth. That was what I was looking for.

Undergrad math I'm already working on it. Our first two years of engineering were basically undergrad math, though, of course, a lot lighter. We went through the most basic elements of Abstract Algebra (groups, laws, stuff like that...), did a fair bit of Linear Algebra and Dynamical systems, and a basic overview of most fields in Analysis (real analysis, complex, harmonic...) but not in details.

We also did Calc and I got a very nice grade in probabilities, but I guess that's not worth a lot.

So, you're recommanding applied maths or applied physics ? That's also what my teachers said, but I don't want to give up on my dreams just yet. I still have two years left to decide/learn stuff. Will do a internship in a lab in the meantime to work with doctors/scientists to see it in details.

Thanks for the answer.

there was a time where everyone was posting these pictures where people are on train rails and it was like "would you kill 1 person or 20 person" or something like that

What is it called, or where can I find these threads again

>>8732575
The trolley problem or dilemma.

>>8731435

Software, even with a very good hardware you wont go anywhere with a stone age AI algorithm

say we have an infinitesimal number called ∆ (I don't have epsilon)

If
|A-B|=∆
then can we say that A=B for any real numbers? (seeing as how A and B are real but ∆ isn't)

>>8722836
What do you think the research labs are working on OP?

>>8732692
how come delta isn't real?

>>8732702
Because it's an infinitesimal so
0<∆<R
by definition infinitesimals aren't real

Can Kerr black holes, or any black holes, compress data? I mean not in the physical form of data but the actual data inside its physical medium.

>>8722836
What's with psychology/language teachers and personality / alternative intelligence tests? I'm fucking cringing so hard right now listening to people talking about these garbage fucking tests as if they have any legitimacy.

What's the basis behind something like Gardner's multiple intelligence test? How the fuck can you measure someone's "music intelligence" based off questions like "how often do you spend playing a musical instrument?"?

It's like determining people's "mathematical intelligence" by asking them "how often do you solve mathematical equations?" or "what's your favourite number? 7 or 5? If you chose 7 it means you're more logical while 5 indicates your mathematical ability".

Has politics destroyed any legitimate definition of "intelligence"?

>>8732707
Wtf im sure this is not true

>>8732815
https://en.m.wikipedia.org/wiki/Hyperreal_number
try google next time

>>8732815
Please excuse his autism. What he's talking about is non-standard analysis, see https://en.wikipedia.org/wiki/Non-standard_analysis

>>8731192
Thanks for the advice; I particularly fancy that part about reinventing the wheel. Do you have any recommendations or easily accessible avenues for keeping an eye out concerning new developments in certain fields?

>>8727190
>Particles are not even at all sides so one part can become more negative and the other more positive, when you line up all these particles pointing the same way you create a magnet
(this can be done by passing a current through the material).

>>8733160

Look for "review articles". They summarize the main findings and open questions of a field, but at a more technical level than popular science books or magazines. They're aimed at other scientists who aren't experts on that particular discipline.

>>8733528

e.g. here's one on quantitative genetics. I'm not an expert in that field (I'm a physicist) but I can read this and get a "lay of the land" for what these geneticists are working on.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2842708/

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Why am I given [math]P(75 \leq height) = 0.55[/math]? I tried to solve it and I didn't need it:

[eqn]
P(75 \leq height | weight > 230) = \frac{P(weight > 230| 75 \leq height) P(75\leq height)}{P(weight > 230)}
= \frac{P(weight > 230, 75 \leq height)}{P(weight > 230)} = \frac{0.43}{0.69} \approx 0.62

[/eqn]

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just fucking how do I get

y=(e^2x-1)/(e^2x+1)

why do I get (-e^2x-1)/(-e^2x+1) instead, ffs

What is the difference between a topology on a space and an algebra on the same set ?

>>8734360
>picture contains variables v and t.
>your message contains variable x

What did he mean by this?

>>8734618
An algebra is completely about pairs of elements and how they interact. An algebra is typically defined as a vector space with a bilionear product.

A topology cares not about pairs of elements, but about any kind of combination of elements and what kind of structure does your topology give those subsets.

>>8734630
>What did he mean by this?
sorry anon, I meant (e^2t-1)/(e^2t+1) and (-e^2t-1)/(-e^2t+1), resp. used to x I guess

I have done the partial fraction decomposition and I get 1/(2(1+v(t))) - 1/(2(v(t)-1))), upon integrating I get

1/2[(ln(v(t)+1))-(ln(v(t)-1)))]=2t+C, somehow it should be 1/2[(ln(v(t)+1))-(ln(1-v(t)))]=2t+C

that's where it falls apart, when solving for v(t), I get (-e^2t-1)/(-e^2t+1), which is wrong

can't tell if I fucked up during the partial fraction part or what

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Have I finally lost it? I think it should be k^2 = 1, instead of -k^2 = 1. Am I going crazy?

>>8734630
Alright, thanks.

Kinda baffles the mind that everybody can invent their own little Algebra(s) like that. Now I'm trying to think of a space with a certain algebra/topology that could have funny properties.

>>8734677

The partial fractions are fine. You should end up with something like:

[math]\frac{1+v}{1-v} = e^{2x}[/math] where we have subsumed the constant of integration into x

[math]1+v = e^{2x} - ve^{2x}[/math]

[math]1 = - v + e^{2x} - ve^{2x} = -v(1 + e^{2x}) + e^{2x}[/math]

And that gives the required result. I think you just missed a minus sign or something.

>>8733664

It's trying to confuse you.

You correctly interpreted 0.43 as a 'joint' probability, not a conditional one.

If it were 'the probability that he weighs more than 230 pounds GIVEN that he is at least 75 inches tall is 0.43', then you would need it.

>>8734739

(-k)^2 = +k^2

k^2 - (+k^2) - k^2 = 1

- k^2 = 1

imho

Why is there no /sci/ thread about all this time crystal stuff? Is it actually no big deal/fake news?

I thought even limited perpetual motion would be a big deal

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Ok /sci/, so I'm a brainlet who is taking my first course in proof-oriented mathematics and this question has me stumped.

Using the axioms in pic I need to prove that |ab| = |a||b|

now on an intuitive level it's super obvious why this is the case, but I don't know where to start to prove it

if anyone could set me on the right track I'd love you forever

>>8735034
Think about the definition of absolute value.
Usually the proof looks a lot like a bunch of cases.
So you'll check when both are positive, when both are negative, then when a is pos and b is positive, then the other way. When you start seeing patterns you can make your proofs shorter.

If you've prove stuff earlier in the chapter, look at those proofs to see if you can use any of them as a lemma or to shorten your proof [(-a)(-b)=ab], maybe...

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What's a good book to get ready for an intro to calculus course, assuming I've already studied calculus in high school?

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In Taylor's Inequality, what is the M supposed to represent? How do you arrive at M?

What happens to a fly flying inside a car? Does it crash with the back window or something?

>>8735466
what happens to YOU inside a car?
fuck all is what happens, unless it suddenly accelerates or brakes

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why the FUCK isn't pic related in the wiki?

Same goes for Functional Differential Geometry by the same author.

I mean really what the fuck

There's the holy trio of sciences all available in MIT quality scheme lisp free education: SICP, SICM and Functional Differential Geometry.

I have a legitimate invention but I don't have the money to apply for patents. Is there anything I can do right now that doesn't require me to spend loads of money?

>>8734782
indeed, i found it, while integrating 1/(1-x), i completely forgot that while substituting variables, a - signs appears

thanks anon

>>8735977
Because hardly anyone wants to learn lisp today, and fewer people want to learn lisp and then go on learning physics. I'd feel weird to recommend it

>>8736061

Get a job, save money. Hire a lawyer.

>>8722836
You mean amputation?

>>8735862
but what if im a fly?

Why is Borelian tribute of R "smaller" than the set of all parts of R ? I'd think they would equivalent. Can you give a part of R that wouldn't fit into the Borelian tribute ? Thanks.

>>8725670
For you...

>>8735366
M is some finite quantity that bounds f. It basically says that it is bounded and not unbounded

>>8736892
I'm assuming you're trying to translate this from your native language because I have no idea what a Borelian tribute is. It sounds like you mean the Borel algebra on R.

The simplest rough answer is that the Borel algebra only allows you to apply a _countable_ sequence of the sigma-algebra operations.

On the other hand, the axiom of choice lets us make not just countable but also _un_countable choices when creating subsets of R.

You should expect that you can make up much nastier sets with uncountable operations than you can with countable ones, and this is true; you can look up something called a Vitali set which is (in my opinion) the simplest example of a non-Borel set (although it is by no means an obvious thing to construct).

>>8737310
>Borel algebra on R.
Yes. Sorry. The term is "tribu Borélienne"

Thanks for the answer. I do have a hard time thinking of non-measurable sets, thanks for the example.

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I'm a brainlet who wants to understand the -1/12 meme.
I figured out I have to understand zeta functions and analytic continuations.
What resources can I use to learn about those?

>>8737383
https://www.youtube.com/watch?v=sD0NjbwqlYw

This video is everything.
I'm doing a small presentation on Zeta monday and I'm using it as a reference.

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>>8722836
how did post eukaryotic cells acquire energy before engulfing mitochondrial and chloroplastic prokaryotes in the endosymbiont theory?

>>8737621
whoops i mean 'pre-eukaryotes' not post lol

how much time does it take to lift an object of mass m a distance x with an engine with power P?

>>8727511

- ( sec(pi/12) / csc(5pi/12) )
=
- ( sin(5pi/12) / cos(pi/12) )
=
- ( cos(pi/2-5pi/12)) / cos(pi/12) )
=
- ( cos(pi/12) / cos(pi/12) )

Fun problem, do you have any more preferably multi-variable Calculus

--DIFFY

>>8737621
photosynthesis?

>>8737675
[math]\frac{mgx}{P}[/math]

>>8737700
thanks thats what i thought. but what i dont understand is how theres power when theres no acceleration because P=mav. If you're pulling something up at a constant velocity isn't nothing accelerating?

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>>8737621

akarin~

>>8737675

Use an energy argument. Lifting an object up requires energy supplied by the engine:
t = (mgx)/P

>>8728891

x= rcos
y=rsin

r= 2 / (2sin - 3cos)

(2sin - 3cos) * r = 2

(2rsin - 3rcos) = 2

2y - 3x = 2

Any more.
--DIFFY

how many books did it take you to learn the calculus?

Is there any reason why you would summarize a bunch of points by taking three points and listing their relative distances from every point, as opposed to just using coordinates?

Like an equilateral triangle could be (0, 3, 3) (3, 0, 3) (3, 3, 0).

>>8737723
first i had to learn the algebra

im tempted to learn the topology soon

Is occasionally having a couple Excedrin as a caffeine pill a bad idea? I have a large bottle due to frequent headaches and am thinking of keeping some in my car for when I don't have time to get/make coffee

>>8737830
yes you should avoid taking it more than necessary. get plain caffeine pills if you want

>>8737839
This. Caffeine pills are cheap as shit.

g-guys why do my heart throbs so much???


could it be love or an actual sickness

>>8737867
do you drink a lot of coffee or energy drinks? maybe you should go see a doctor

>>8737867
move to japan, rather than throbbing it will dokidoki instead

>>8737882

maybe :( ive been drinking MONSTER for the past few days, now i cough non-stop

but the past few days i feel like an actual non-brainlet :/

>>8737830
Acetaminophen is hepatotoxic.

>>8737889
>i feel like an actual non-brainlet
>:(
>:/

Your brain is fooling you

>>8737923

are you greentexting me or expressing anger my scientific friend? the >:( and >:/ specifically

Hey, /sci/ bros.
My question is actually an advice I'm needing right now, but I don't want to post it on /adv/ (all they know about is relationships) and I don't think that creating a whole new thread for it would be necessary.
So, I've recently decided to change my major to mathematics and this semester I chose to course real analysis. The problem is that I'm not used to writing/reading proofs and I still haven't coursed discrete mathematics (even though it's not a prereq for real analysis, it is still a good introduction to proofs and real math).
I'm able to understand the concepts of real analysis up to now, but since I'm not used to writing/reading proofs, I'm taking way too long to understand things, which is kinda making me perform poorly on other classes I'm currently attending.
Should I drop real analysis and wait until I have a more solid abstract math knowledge?

>for every action there is an equal but opposite reaction

Is the opposite reaction instantaneous?

If (assuming you could move infinitely fast) a ball is dropped on the ground could you move it after it has transmitted force into the ground but before the ball experiences the force?

>>8723241
Ballistic vectorials.

>>8737724
Distances are invariant under rotation and reflection. So finding whether two sets of points are similar (in the geometric sense) doesn't require first transforming them to a common orientation.

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>>8722836
pic related
How i read that expression ?

>>8726126
And it's still wrong. It's 3-ethyloctane

Given that about 2.7 trillion digits of pi are known could one calculate the circumference of a circle with more precision than the smallest bit of matter?

>>8739107
You unite all the U_alphas where alpha is an element of A.
This union is an element of C

>>8739107
U is a set of sets (call them u's) that is indexed, and the indeces are sets themselves.
A is a set of sets which are all among those indices sets
C is some big set of class (not so important)
The expression on the left hand side of the "is in C" part is a union of sets, namely all those u's that are specified by the index set A.

Let me cook up an expample

a = {1,2,3}
b = {9001, 9002}
c = {7,9}
A = {a,c}

Let's define some more sets for auxiliary purposes
u_a = {"one man", "two men", "three men"}
u_b = {"seven anons", "fuck your mom", 77}
u_c = {"memes"}
u_d = {"why not"}

Usually U will be some set that contains a whole bunch of u's and some are indexed like above
And then define

U_a := u_a
U_b := u_b
U_c := u_a
U_d := u_a

Now the union of U_i w.r.t. i in the index set A is
{"one man", "two men", "three men"} union {"memes"}
i.e.
{"one man", "two men", "three men", "memes"}

and the pic claims that this set is in some big set C

set or class*

>>8737621
Predation perhaps. Phagocytosis and the breakdown of their cellular components can also provide energy. It's like eating, but then eating living organisms and on a unicellular basis.

>>8739147
>>8739150
thanks , i just start read Basic topology.Armstrong
i was think that expression means union of all element of U_alpha

I got this algorithm that is used to multiply big numbers faster than the standard grade school algorithm.
It's an algorithm that uses divide and conquer to use as many "cheap" operations as possible to make the algorithm have a better time complexity.
I just don't understand the whole procedure, can someone explain the pseudo code in simple terms.
[code]Algorithm multiply(u,v,threshold)
Input: u, v big numbers stored in an array
threshold - the maximum length where it is "cheaper" to perform ordinary multiply
Output: a big number that is the result of u*v

n ← max(digits(u),digits(v))
if u=0 or v=0 then
return 0
else if n<=threshold then
return ordinaryMultiply(u,v)
else
m ← n/2
x ← u divide 10^m
y ← u rem 10^m
w ← v divide 10^m
z ← v rem 10^m
r ← multiply(x+y,w+z)
p ← multiply(x,w)
q ← multiply(y,z)
return p mult 10^(2m)+(r-p-q) mult 10^m + q[/code]

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>>8722836
there is any topology book for non math?

>>8722836
There is research into preventing metastasis but with most medicine the money and funding is in reactive medicine rather than proactive because that's how society loves to solve problems.

University Physics or Halliday's Fundamentals of Physics?

I need to get a new physics textbook.

I need a good text book on Special relativity that introduces tensor notation, or any book that explains how to use tensors that isn't just "this tensor lowers the index" bullshit

>>8736069
it's so cool though, it at elast deserves its own niche spot on there. it's not even in the comp sci part of the wiki either.

>>8739264
Untyped functional programming just seems exhausted.

https://youtu.be/pCceO_D4AlY

I there really only 1 sort of intelligence when it comes to problem solving?

>>8737889
>but the past few days i feel like an actual non-brainlet :/
bro i feel you, since i started drinking higher quality coffee it's like i've been reborn into a top tier playa

>>8738682
as far as newtonian physics are concerned it's instantaneous

I've did some reading on division by zero. My conclusion is that a/0 is only undefined because it would be very inconvenient for mathematicians if it were (e.g. there is no b such that b0=a where a!=0, and it leads to paradoxes etc).

This is probably a reasonable thing to do (pretending that a/0 is impossible allows for useful mathematics to be built on top) but it doesn't seem very rigorous either. In particular, it seems wrong that division by zero is so often presented as being inherently impossible or nonsensical. It's perfectly possible and makes perfect sense, it's just that it would ruin a bunch of other maths if we allowed it to be so.

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>>8722836

hello
I need help with this problem

Let tan θ = 15/8

with θ in QI and find the following.

sin 2θ

>>8739448
it is defined, in several places,and you would know if you took real or complex analysis.

check out the riemann sphere

>>8739258
Please respond

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>>8739258
>Halliday's Fundamentals of Physics
why u cant take both?

>>8739470
find the value of θ whose value is 15/8 (protip you have a button on your calculator that does this for you)
double check that it's in Q1
once you know what θ is you literally just push butan on calculator to calculate sin(2θ)

>>8739564
*whose tan is 15/8

>>8739564
My assessment will not accept a decimal, but i just figured it out.

Thanks for reminding me of this though, it didn't even cross my mind to check it on the calculator

>>8739090
But does this type of summary have a name, and are there transformations that use it?

Is it possible for narrow beam wireless transmission within the atmosphere to be mostly undetectable? For optimal fidelity and practicality, what wavelength would you use?

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https://www.youtube.com/watch?v=e-a8auViFM0&list=PLelIK3uylPMGzHBuR3hLMHrYfMqWWsmx5&index=2&t=2564s

when the nigga did a couple of operations on the group S_n, the permutation group of n letters, what is the identity of this group?

seems to me that the identity of this group is a permutation of that grup where 1 - 1, 2- 2 and 3 - 3 but why doesn't he draw that??

>>8740053
You're correct, the identity of a permutation group is just the permutation that maps every element to itself.

I can't tell you why he didn't draw it, I'm not the lecturer. Presumably he either thought it wasn't worth writing out in detail or he simply forgot.

>>8740128

i don't quite understand what's this group (?) actually is, is it a group of all possible bijective operation on on the set (1,2,3) ? so like {1 - 1, 2 - 3, 3 - 2 } is a set of possible operation on {1,2,3} which itself is a set in the group???

its really hard for me to fully follow his lecture

Can you multiply sand piles by each other?

>>8740183
You're correct, literally speaking the elements of S_n are the bijections from a set with N elements to itself.

When you think about what it really means to re-arrange the set {1,2,...n} all you're really saying is "what position does the 1 go in? where does the 2 go?" etc. which is just a function.
Of course it must be bijective because every number goes in one and only one spot.

However you shouldn't say that
>{1,2,3} is a set in the group
The elements of the group are not sets. They are functions.

>>8740231

>The elements of the group are not sets. They are functions.

yea my bad, i was trying to refer to the set that this group is working on given some n, what is this called?

>>8740252
As far as I'm aware there is no name for {1,2...n}.

You should realize though that what's inside the underlying set has nothing at all to do with the definition of S_n; there's no difference between permuting {a,b,c,d,e} and {1,2,3,4,5} and {dog, banana, chair, dick, 37}

There is only one S_n which is exactly the same for _any_ set with n elements. We just use {1,2...n} because it's convenient.

>>8739470
tan(theta) = sin(theta) / cos(theta)
=[opp / hyp] / [adj / hyp]
=opp / adj

=>opp = 15, adj = 8

=>hyp = sqrt(15^2+8^2)
=17

sin(2*theta) = 2*sin(theta)*cos(theta)
=2(15/17)(8/17)
=240/289

>>8739135
Can no one answer?

>>8740290
Depends on how large the circle is. If you constrain it to the size of the universe, then yes, no question.

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Can someone help me? I know that x-1 = 0 is the line that is on the plane [math]\pi[/math] but how do I find a normal to the plane so that I can dot product the normal and a vector to get the eq of the plane [math]\pi[/math] ?

>>8740306
D is the correct answer, yes?
(x + y + z) - 2 * (y + z) = x - y - z
(1) - 2(0) = 1
Therefore, x - y - z = 1.

>>8740314
I dont understand whats happening, can you explain? And yes D is correct

>>8740319
You're subtracting the first equation by twice the second equation.
x + y + z = 1
-2(y + z = 0)
x - y - z = 1 - 2(0) = 1

>>8740323
I meant to draw a line between the second and third equations here to make it clear it's a subtraction:
x + y + z = 1
-2(y + z = 0)
____________
x - y - z = 1 - 2(0) = 1

>>8740323
>>8740324
But why are you doing that though? Why are you subtracting a plane with another plane and how does that give the equation of the plane [math]\pi[/math] ? That doesnt make any sense to me why is the intersection of the two planes not taken into account and done something with point P?

Is it not possible to find the equation of a plane through a line and an arbitrary point?

>>8740296
so after a while nothing physical is being measured? Is this problematic?

>>8740329
>Is it not possible to find the equation of a plane through a line and an arbitrary point?
Yes, but it's not necessary in this case. If you'd like to see how you do so, read this:
http://tutorial.math.lamar.edu/Classes/CalcIII/EqnsOfPlanes.aspx

>But why are you doing that though? Why are you subtracting a plane with another plane and how does that give the equation of the plane π?
There are multiple valid equations of a plane. I don't approach this geometrically, but logically: the plane contains the intersection between two equations. If there is a point where both equations are satisfied, then it is on the plane π. I can exploit this fact to match the answer in part D, thus proving that claim is true.

>>8740334
No; you would need to know the diameter to the same error (divided by 2π) for the result to be meaningful. When I say a third of a meter, I am not saying the measurement is 0.33333333333... m with infinite precision.

>>8740361
Do the variables k, j, q, r have any special meaning in math? Many text books seem to prefer them.

File: linear_alg_question.png (19KB, 698x184px) Image search: [Google]

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So far I have shown that the product AX=XB, where B is a diagonalised matrix with diagonal entries lambda_n. I've then shown that A is the product XBX^-1. Is this correct? What must I do from here?

>>8735366
you can choose the max value of |d^nf/dx^n| for it.

>>8740379
Possibly, but I think they just want to group letters which are close together to represent multiple instances of the same object. Point starts with a p, so they use p and subsequent letters to represent points. You naturally associate p with q whereas you probably wouldn't associate p with g.

>>8740394
hint: Ax = λx => AX = λX

>Find three consecutive odd integers such that their sum is five more than four times the largest integer.
It gives the answers of -15, -13, and -11. But it doesn't show how it got there, and my teacher never covered it. How do you get to those numbers?

Anyone know how to draw a tangent line to a function with numpy? Can't believe this shit is this hard to find out

I made an electromagnetic coil and for some reason the paramagnetic beads I'm using aren't attracted to the coil. Should I go with bigger beads to increase the attraction?

>>8740454
I know this is SQT, but you should really know how to do this. Try writing the second and third numbers in terms of the first.

>>8740476
Maybe there's an easier way, but first find the slope:
[(f(x + h) - f(x - h)] / (2h)
Then use the coordinate of the point you want and plug it into y=mx+b.

>>8740491
I don't want the line occupying the whole width of the graph I only want a reasonable sized line and I want more than one tangent (28)

>>8740502
I don't know the specifics of numpy, but surely you can restrict either the domain or the length of the tangent line with some programming. Write a function to do it multiple times.

>>8740510
Thats the thing there literally isn't unless someone who knows how to do it, been fking searching this shitty documentation on numpy for 2 hours and I can't find something simple

>>8740523
Found this, might help:
http://stackoverflow.com/a/21357666

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Currently tying my noose, help me out fellas.

What is the biggest area of mathematics that hasn't truly been connected to nature yet?

>>8740751
Almost everything in math has at least one physical application.

>>8725700
Heat is transfered by termical radiation and by direct contact between molecules, and the second way is much more potent. That's why in cosmic vaccum you would not freeze instantly, because there is not much atoms to which you could transfer your heat.

>>8740751
Abstract arithmetic

>>8726431
Physical Chemistry by Atkins, if you want to broaden your knowledge on thermodynamics

Is there a correct word to describe fungi and plants as food?

I don't think the word vegetable is correct; Mushrooms =/= Plants.

>>8727446
In Polish nomenclature it's respectively E with lower index P, and E with lower index K.

>>8740805
Why not just study thermal physics/statistical mechanics then?

>>8727511
Is the Secans function even used nowadays? I've never found any significant usage of it.

>>8732542
We don't even know where and how long-term memory is being stored (short-term is residing in Hippocampus gland), so the mechanism behind forgetting is also unknown.

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>>8732575

>>8737867
Try to eat better quality meals, get at least 7 hours of sleep per day, cease consumption of caffeine and try to measure your blood pressure and heart ratio during different periods of day. If you really think something is wrong, visit a cardiologist.

Question:

I need to know some kind of philosophical question/dillema/problem which I could use to strike up a conversation with stranger, which would lead to further discussion.

>>8740863
would you rather eat shit or shit into someone's mouth?

>>8740863
>▶
whats the meaning of life?

Is [math] e^{\pi x} = \left ({x}-{\frac{{2} {\emph{W}(\frac{\pi}{2})}}{\pi}} \right )^2 [/math] true?

Without sounding like \pol\, is there any explanation for the racial difference in IQ tests besides racism of the test?

IQ tests don't seem like they would have any method for testing White vs any other race, so why do minorities suffer from lower scores?

>>8741018
>IQ tests don't seem like they would have any method for testing White vs any other race, so why do minorities suffer from lower scores?
Not all minorities suffer from lower scores, only blacks. Asians and Jews (especially Ashkenazi Jews) score higher than whites

>>8741020
Then once again, why? what would cause this?

Also FYI Hispanics apparently suffer compared to whites.

>>8741026
https://en.wikipedia.org/wiki/Race_and_intelligence
https://en.wikipedia.org/wiki/History_of_the_race_and_intelligence_controversy
https://en.wikipedia.org/wiki/Ashkenazi_Jewish_intelligence
take your pick

it seems to suggest a significant 'nurture' effect alongside whatever 'nature' effect comes into play

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Anyone mind helping me understand SVD? I can't understand what the "D" is, pic related.

I h(https://docs.scipy.org/doc/numpy/reference/generated/numpy.linalg.svd.html) to return me the U and V component but it gave me an "s" component instead of the "D" one which it says its containing the singular values for every matrix which I have no idea what that means.

What am I supposed to do with this "s" component to get the D component?

Im having trouble understanding pic related "D" component..

Dear god please someone tell me how to show more than 1 image in pyplot... every time I try to show another image the next one overwrites, why is this so difficult.

>>8741018
in the US? race is tied to socioeconomic class
black people are more likely to be poor and live in inner cities which will have shittier schools etc

>>8741041
Create an empty m*n matrix of all zeroes and populate the first 100 elements of the main diagonal with your "s" vector.

>>8741224
Yea I got it a while ago I was having a brain fart, tried to delete the post but it was up for too long...

Any idea about >>8741208 this though?

Right now its printing images underneath each other and I don't know how to make them side by side

Code:

f1 = plt.figure(1)
plt.axis("off")
plt.imshow(img, cmap='gray')
plt.show()

f2 = plt.figure(2)
plt.axis("off")
plt.imshow(u)

plt.figure(3)
plt.axis("off")
plt.imshow(d)
plt.show()

plt.figure(4)
plt.axis("off")
plt.imshow(v)
plt.show()


This is really silly but Im new to numpy and I can't google a clean solution

Where can I find some hard but explained problems on statistics?

My professor is notorious for her hard questions and the class is interesting. I want to study but couldn't find a good source on creative problems.

Here are the subjects we are responsible for:
-Experiments, Models, and Probabilities
-Discrete Random Variables
-Pairs of
Random Variables

I'm looking for a distance of two vectors. I ended up with this equation and I need to find X and Y for whose the square root have the lowest value.

[math]\sqrt{166+122x-190y-74xy+26x^2+89y^2}[/math]

The original vectors were
[math]
(9, -2, 0) + span(4, -3, 1)
[/math]
[math]
(0, -7, 2) + span (-2, 9, 2)
[/math]

I plugged them into the ||A-B|| equation and this came up. How can I solve this? I need a second equation since so far I have one equation with two unknowns, but where can I find it?

Noob studying phyiscs, biochem major.

Isn't the thought of a non-contact force a little weird? Or rather, is there such a thing as a contact force at all? What actually separates long-range electromagnetic forces from the short-range push of electron clouds against each other?

Maybe soft jazz will help

>>8741367
>long-range electromagnetic forces from the short-range push of electron clouds
Electro-magnetic force is several orders of magnitude stronger than gravity, but is virtually inexistant in the macroscopic world because charges strictly compensate themselves.

>Isn't the thought of a non-contact force a little weird?
Drop a object from a height. It will fall, yet there's no contact.

> Or rather, is there such a thing as a contact force at all?
Yes, when somebody pushes you, for instance.

>>8741387
I know that's 'contact force' as contact is defined traditionally, but on the atomic level, there is no actual contact of mass-bearing particles, right?

>>8741390
I'm just a materials engineering student. This is too advanced for me, I'm afraid.

But as far I know, neutrons and protons inside a nucleus are in "contact", though it's really hard to conceptualise. Even 100 keV electronic microscopy cannot the nucleus (which is about several picometres), only the atom itself (which is 1 Angstrom, ie 0.1 nanometre.)

>>8741393
Thanks for answering, though. I'm just wondering if traditional 'contact' between two objects that's essentially electron clouds pushing in entropically unfavored ways is any different fundamentally to the other electric forces that have to do with free-flowing electrons.

>>8741397
There are four fundamental forces :

- Electromagnetism
- Gravitation
- Weak interaction (radioactivity)
- Strong interaction (what holds nucleus together)

Electrons only ever play a role in electromagnetism, which in turns does play a role in the geometry of molecules (covalent liaisons, ionisations, and so) which order matter.

But electrons have no role in mass : it's a common acceptance that their mass is virtually null.
Also, fyi, even the position of electrons around the nucleus is not driven by electromagnetism. If it was, electrons would orbit uniformly around the nucleus.

You might know that any orbit object is accelerated. But any accelerated object is subject to a force (F = ma), and any object subject to a force emit energy in some kind.

Which would means that the electrons would, eventually, stop orbiting. It's been calculated that the average time before collapsing would be 10^-10 seconds. So it's safe to say it's not electromagnetism which holds electrons around the nucleus. (it's actually spooky quantum mechanics)

Can someone explain to me what vacuum energy is? What kind of energy is there created? The most fundamental particles? Or is there a threshold on how chopped up the particles that phase in an out are ?

>>8741393
Angstroms are kinda obsolete nowadays, I'm materials engineering student too, and on my Uni using them is strictly forbidden.

>>8741585
Well don't tell that to my optical spectroscopy professor :^)

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how in gods name does this look in a T,s diagram, especially the red circled part?

pumps are isenthalpic, turbines are isentrop

ill reply to this post on how I think it looks, can sameone tell me how wrong I am?

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>>8742317
i dont know where to put 4, any ideas?

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>>8722836
There is a plant that is really good at killing some types of cancer, yes it is dandelion, but we need to legalize hemp somehow to treat another kind of cancer.

>>8741343
First, I'm not sure that your equation is correct; I get:
89*y^2 + 26*x^2 + 66*x*y - 46*y + 38*x + 110

Basically, you need to use a change of variables (express x,y as an affine transformation of u,v) to get the equation into the form a*u^2 + b*v^2 + c. That has a minimum value of c when u=v=0.

E.g. for the above equation, setting
x = 56*v + u - 2
y = -7*v - u + 1
gives:
49*u^2 + 60025*v^2 + 49

Clearly, this has a minimum of 49 when u=v=0, at which point x=-2, y=1

Has cellular automata actually been useful for solving any problems in math? Like a relation between two sets that can be expressed through cellular automata rules?

If photons can be redshifted by gravity, doesn't that mean they are losing energy? If so, where is the energy going?

How the fuck I solve this?

No l'Hospital

[math]lim_{x\to 0} [\left (\frac{x-sinx}{sinx} \right)^2\,cos \left (\frac{1}{x} \right )][/math]

>>8742631
if you don't want l'hopital, then sketch it nigger

Let a, b, and c be integers with a ̸= 0. Prove that if ab|ac, then b|c.

>>8742631
x/sinx-1 --> 0 and cos is bounded

>>8742703
Please elaborate.

>>8742692
Write out the definition of "|" (i.e. write out what ab|ac means)

Then it should be pretty simple

>>8742729
[math]\frac{x - sin(x)}{sin(x)} = \frac{x}{sin(x)} - 1[/math]
as x approaches 0 sinx becomes approximately equal to x, so this approaches [math]\frac{x}{x} - 1[/math], aka 0

[math]cos(\frac{1}{x})[/math] is always a finite number, it doesn't approach infinity

0 * (any non-infinite quanitity) is 0

>>8742828
B-But its
[math]\left ( \frac {x-sin(x)}{sin(x)} \right )^2[/math]

not
[math]\left ( \frac {x-sin(x)}{sin(x)} \right )[/math]

I really don't get it

>>8742847
0^2 is still 0

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I can't find the issue with the setup for my hydrostatic force problem. Can someone point out the issue?