SQT - Stupid Questions Frog

I rolled a 1 on my physics lab group. Should I drop out, kill myself or both?

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Some data I've collected follows an inverse bell curve pattern. Technically I guess the distribution would be bimodal.

What descriptive statistic would you use to report results on such a distribution?

Doesn't seem like the mean would be representitive of the data if it has the smallest frequency in the histogram.

Or do I need to transform this shit?

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Could a group of fish, such as cod, take to the skies after the demise of the birds?

If I have a certain number of molecules as per Avogadro's constant am I safe to assume that the number of atoms is the number of molecules multiplied by the number of atoms in each molecule? Seems obvious but my retarded book won't tell me and I want to be sure.

honestly there should always be a SQT stickied and just archive at 300 posts

would probably alleviate the bulk of homework threads

>>8617749
How many dogs do you have to fuck to learn doggy style?

>>8618052
A true academic would teach them human style.

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>>8617749
i dont feel like doing any integrals today but this should get you moving in the right direction

before the explosion you have a prism sitting in a zone with ambient pressure; we can assume the pressure inside the prism is the same as ambient pressure because the prism is not spontaneously exploding right now

when the bomb goes off, air pressure around the bomb increases
this spherical zone of increased pressure eventually reaches the prism and begins acting on its surface to compress it

at any given moment, the surface of the prism that is inside the explosion is being compressed according to the pressure difference between the inside of the prism and its surroundings

assume uniform density for the region we're considering "inside the explosion"

Assume that the bomb instantly explodes all of its contents; in other words, the explosion has a constant mass, but its density decreases over time as the shell expands

Then decide how far away the prism is from the bomb and how big the prism is.

>>8618108
That seems a tad elaborate.
I'm just talking about getting the area of the prism from the point of view of the explosion: Kind of like the angular size of a celestial body, but a prism-suitable equivalent.
Doesn't have to be accurate, just not absurdly innaccurate, since this is for a game.

>>8617950
Fish gills evolved into insect wings, so yes.

>>8618052
You'd learn more from getting fucked by one.

>>8617969
It doesn't say because that's common sense.
If you have a billion boxes containing ten balls each, you can be pretty sure you have ten billion balls.

Unless you count the balls in pairs if they're still in the scrotal sac.

Given a square or circle (whichever makes the maths simpler) of known area facing towards the viewer, how to I calculate the size it appears for the viewer?

If all body cells are replaced every 5 years or so, then why do scars last a lifetime?

>>8618439
For a circle, the "size" basically means the solid area of the cone formed by the circle and the viewpoint.

en.wikipedia.org/wiki/Solid_angle#Cone.2C_spherical_cap.2C_hemisphere

>>8618462
The cells forming the scar tissue are replaced by more of the same, not by whatever was there before the scar.

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Trying to get the residue of [math]\frac{e^z}{1-cos(z)}[/math] , but by following the formula for simple poles it doesn't work. I managed to get it from its Laurent series expansion, but I don't understand why would such a function be problematic. Thanks in advance anons, if you see any problems with the process feel free to instruct me.

>>8617749
>What's a decent approximation for how much of an explosion's force a prism would be exposed to?

I'd imagine that it would be roughly proportional to it's projected area.

>>8618611
I'm not looking to find the volume of a cone though.
I'm trying to find the size of the object in like, square degrees.

>>8618633
That's the hard part though, getting the projected area.

>>8618630
do you not know what simple pole means?

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Are there limits on what kind of major/minors combinations one might take?

How bad of an idea is doing a bachelor's in microbiology, like virology?

got a question for you: we all know that the fundamental group of a torus is ZxZ, what does it became if you join two of its points(by a curve, or just identify them)? can you find its universal covering space? (rem. for the torus is just a plane, with deck composed of integer translations in two directions)

>>8617749
Sorry for the stupid question but... What if something's mass is zero?

By zero, I mean m = 0, not something close to zero like photon. I tried Google-ing it, but could not get the good answer.

>>8618748
>not something close to zero like photon.

Photons have 0 mass, not near 0, but actually 0.

>>8618750
It has zero rest mass, not zero mass, right?

>>8618630
It's a double pole at zero. You can see that from your series expansion.

>>8618751
No, there is no frame where the photon is at rest, that would violate the principle of relativity. Moreover there is only one kind of mass and that's the invariant mass, ie the square of the energy-momentum 4-vector.

The idea of a "rest mass" and "relativistic mass" leads to lots of problems, and can be removed by suitable definition, for a simple example look at [eqn] \vec { p } = \gamma m \vec { v } [/eqn] You could put the [math] \gamma [/math] on the mass, or on the velocity. Putting it on the velocity is perfectly fine.

What function or symbol captures this behaviour? Like an anti-kronecker delta

[math]\delta ^{ij}=\left\{1\:if\:i=j,\:0\:otherwise\right\}\:???=\left\{0\:if\:i=j,\:1\:Otherwise\right\}[/math]

>>8618776
1 - \delta_{ij}

>>8618777
A hurr durr thank you for curing my retardation

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What did he mean by this?

>>8618794
lol jk I was only trolling

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so I decided to learn maths on my own, starting from basic shit, I'm trying to prove why pic related has "no solution" I only got halfway. I checked it on wolfram alpha and it gave me a longass non solution

where do you stop?

>>8618801
x - root(x-2) will always be less than x + root(x-2), so it'll never be greater than 1.
Are you trying to do a formal proof?

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Help me understand this pls /sci/

Aren't those highlighted sentences contradictory?
Am I missing something?

>>8618838
Nvm I get it now
Fucking brainfarted

>>8618838
A lot of people get tripped up on the second property you posted at first.

Probably you understand the first one; if I claim something exists in the empty set that satisfies P, obviously it's false. Nothing exists in it at all so clearly you can't find an example.

The second one is something like this; I claim every element of { } is an elephant. Which objects am I claiming are elephants? None at all.
This is why it's vacuously true; when you say something about "all elements" of the empty set you aren't actually describing anything so you can say whatever the fuck you want.

>>8618857
Thanks anon
It's also nice to hear that other people get that brainfart too kek

Also it sort of helped me thinking [math]\exists[/math] means that there is at least one, so when you negate it it fits the context

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>>8617749

What the fuck is a digital motor?

>>8618885
A buzzword.

How do i get good in Math in general? Is it possible to self-teach by starting below?

>>8618899

These days there are pretty good online resources that will walk you through it from easy stuff to hard stuff. And they're free.

>>8618834
nah, just trying to "solve it" have something that can say that is has no solution, like what you said

how you put it it makes PERFECT sense, thank you

this might be a bit unrelated, but how do you just train your mind to "see" those (mathematical) things that make you understand maths better? like it took me some time to understand inequalities and absolute values, but then I just saw it and it was so stupid easy

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So, the black dot IS part of the red set (the result of a cartesian product) but not part of the blue set (a line which intercepts with the interior of an open circle so the boundary is not included).

My question is, can the separating hyperplane theorem be applied? Both sets look disjoint, convex and non-empty, but I can't imagine a hyperplane separating them.

>>8618930
Imma different dude but I would say practice practice practice. Maths is a skill and the more you do it the more familiar you become with how it works until you don't even have to 'think' to recognise things like that, you just instantly know because you've seen it before.

It's like a dude speedsolving a Rubiks cube, he doesn't really think much about what he's doing, he's just practiced so much he can quickly recognise some pattern of colours and then his muscle memory does the work from there without him thinking about it

>>8618945
thanks, my man

>>8618996
The LaTex gods don't favour you today

>>8618998
They never seem to favor me..

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anyone willing to help me with any?
need to prove with epsilon delta and completly lost.

>>8618996
Use [ / math ] instead

I am given the following open loop transfer function:

[eqn]G(p) = \frac{3}{(p+1)(2p+1)(4p+0.5)}[/eqn]

And am ask for which additional constant [math]K[/math] the closed loop system becomes an oscillator and at which frequency [math]\omega_0[/math]

----------------------
My reasoning:

The closed loop system oscillates when the open loop system becomes -1 for [math]\omega_0[/math].

So

[eqn]\angle{K \cdot G(\omega_0 \cdot j)} = \angle{G(\omega_0 \cdot j)} = 180\degree[/eqn]

which gives you [math]\omega_0[/math]

[eqn]|{K \cdot G(\omega_0 \cdot j)}| = 1[/eqn]

which gives you [math]K[/math]

I want to be able to solve these equation quickly with a TI nspire CAS machine (without additional software). So basically just solve system of complex equations. But when I try to solve the first equation it already gives me this apparent nonsense:

1=-2/(sign(G)-1)

(with G := G(w*j) )
---------------------------

So, is my reasoning wrong, or is my is my use of the calculator wrong?

>>8617749
[math]\textrm{text}[/math]

>>8618721
> I'm trying to find the size of the object in like, square degrees.
Solid angle is measured in steradians. Which is what that formula gives you.

>>8617829
can't u just take the inverse to solve the problem

>>8618735
anything in biology in its name is probably a bad idea unless you 100% know this is your passion

is there anyway 1/3 can be a natural number, is it not a rational number?

>>8618735
>How bad of an idea is doing a bachelor's in microbiology, like virology?

can you really do a bachelors in something so specialized? aren't those more like masters? or is that how it works in us of a

>>8619074
You can multiply it by 3

>>8619080
I am such an imbecile, I was checking at the wrong answers

R3posted from other thread, hoping for a response.

Help me /sci/

Math brainlet here, but trying to get better.

What does 1 minus a ratio represent? For instance, we have 3 Blue Balls and 4 Red Balls. That means we have 3/7 chance of drawing Blue and 4/7 chance of drawing red. But there are 3:4 Blue : Red balls. So 1-(3/4)= 1/4. What does one quarter mean in the context of the balls? A ratio? A likelihood? Plz help.

relavance: the equation on the screen at https://youtu.be/-q7EvLhOK08?t=322 [Embed]

>>8619270
I don't think it represents anything in particular, it just happens to appear in that equation.
Maybe some mega nerd will know that the 1/4 in that context represents the oggooly-boogly stationary torus state in quaternion meme space as part of Discrete hyper-dank theory but there's nothing obviously meaningful about it

I'm a math major but I haven't taken probability since high school, so I'm just asking this question for my own curiosity. If we start at 0, and we flip a coin, and if we get heads, get +1 point, and tails, -1 point, what's the expected number of flips to get to 5 points, given that we can't go below 0 points? I've found a bunch of papers on random walks but none of them seem to talk about what happens if you have a lower bound you can't go past.

What are those balls under my mouth skin, like at the bottom? Why is there are pair of bollocks under my tongue?

>>8619578
Related, why are there two little slit-like holes on the roof of my mouth?

>>8618801
first, use the substitution x = 2cos^2(t)
then, 2cos^2(t)+3sqrt[2]isin(t)=0
this has solution
t=2(npi-itanh^-1(sqrt[2]-sqrt[3])) for all integer values of n
so choose n=0 to get
t=-2itanh^-1(sqrt[2]-sqrt[3]))
because x=2cos^2(t), plug t back in to get

x = 2cos^2(-2itanh^-1(sqrt[2]-sqrt[3]))

and by the wolfram alpha black magic theorem, we get
x = 3 (seriously, how the hell does it do that?)
but clearly, if x=3, then 1/2 = 2
therefore there are no solutions over the numbers

How can I stop being a brainlet?

Can we mathematically describe a scenario where you're rotated along the x-t plane but staying in the same location?

What's a good way of generating stars of random size and temperature?
The problem is that the two are interrelated in a non-linear way; small stars are cold, absurdly huge stars are cold, medium stars are warm, and giant stars seem to be whatever they want.

>>8620260 (You)
nevermind, i figured out how. it's just

[math]
x' = x \cosh \zeta\\
t' = t \cosh \zeta + x \sinh \zeta[/math]

I hope I did't fuck up the latex

Quick stats question, if you have a constant, b, does
Expectation(b^2) == Expectation^2 (b)?

Also, any tips to get better at writing LaTeX?

>>8620214
Read! If I remember correctly, the /sci/ sticky has a ilnk to a ton of textbooks

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>>8619307
There was a FiveThirtyEight "Riddler" problem similar to what you're asking (see pic related)

I'm not entirely sure about why you would need a "recurrence relation" (or even what that is), but hopefully the link may help you:
https://fivethirtyeight.com/features/solve-the-puzzle-stop-the-alien-invasion/

What's a function that produces 0 from 0 and 1 from infinity?

>>8620514
{(0,0), (infinity, 1)}

Is a double major a good idea or are they generally looked down upon?

I was thinking about double majoring in computer science & engineering and electrical engineering but the uni I plan on going to doesn't allow any double major combination between CS, CE, and EE. So I was opting for a CS and mechanical engineering double major. My plan was to go to school for CS work a bit then go back to get a BS in ME. I'd like the ability to both design and program the machine I'll work with. I'm interested in robotics and A.I. and I want the ability to be able to do work in both but I do lean toward AI.

Would a double major be a good idea? Is it unlikely to work on a project where one person works with both hardware and software on a machine so am I better of focusing on one? Would CE be better even though I prefer software?

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>>8620514
And does what in between?

f(t)=e^-t-e^-kt for k>1 is 0 at t=0 and ->0 as t->inf, peaking at t=log(k)/(k-1).

>>8619307
It depends why you can't go below zero. I.e. whether you just ignore any tails if the current score is zero, whether you count the tail as a flip but don't adjust the score, or whether you discard the entire sequence (i.e. calculate the expected value for sequences where the score never goes negative).

In either case, it's easy enough to write a simulation to produce an empirical result so that you can check whether a theoretical result is likely to be correct.

If we know [math] \sum_{i=1}^{n} a_i [/math], then what do we know about [math] \sum_{i=1}^{n} \frac{1}{a_i} [/math]?

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You guys are smart

I wish I could understand you

>>8621255
not difficult to understand if you go through each term or concept 1 by 1, it is just daunting at first

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A couple months ago I went through a summer calc class since I failed calc back at my regular university. When I was there, the professor recommended some course he liked that aimed to solve normally calculus problems using algebra. I can't for the life of me remember what the class was but I don't think it was differential equations.
Does anyone happen to know what the hell I'm talking about? It sounded like an interesting thing to study or read about so I'm searching everywhere I can.

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Can someone help me here?
Why is this function's graph defined in x = 1 if x = 1 is not in its domain(neither is x = -1 and x = 2, which clearly are not defined in this graph).

can't seem to understand this simple one-line proof that a field of rational functions isn't an archimedian ordered field.

archimedian fields require this condition to be met
>for all x,y belonging to P there exists a natural number n such that n*x > y

the proof:
>let x = 1/t (belonging to P) and y = 1 (belonging to P). Then for every natural n: n*x < y

I get that 1/t has to be less than 1, but plugging in actual numbers quickly leads to a contradiction, unless 1/t is infinitesimal. I can't just assume that, though, right?

it doesn't work for any t < n

i have this non-homogenous 2nd order differential eq. of oscillating motion
[math]y''(t) + y(t) = sin(t)[/math]

and i want to transform this into a first order system of the form

[math]x' = f(t,v)[/math]
[math]v' = g(t,x)[/math]

to apply a semi-implicit euler-scheme

how to transform this?

>>8621409
forgot IVP:

[math]y(0) = 0[/math]
[math]y'(0) = 1[/math]

>>8621389
Read up on the ordering used between rational functions. It's not what you would expect.

>>8621384
It isn't. There's a hole there. But Wolfram Alpha doesn't render that hole explicitly.

Can someone help me out on the following:
Let [math] X_1,...,X_n [/math] be an iid sample, uniformly distributed on [math](0,\theta)[/math] and [math]M:=max(X_1,...,X_n)[/math].
For [math]0<\lambda_1<\lambda_2<1 [/math] and [math]\lambda_1^2-\lambda_2^2 = 1-\alpha[/math] show that [math][M/\lambda_1,M/\lambda_2][/math] is a [math]1-\alpha[/math] confidence interval for [math]\theta[/math]

>>8621423
Thank you, anon.

>>8621423
okay I rechecked the ordering criteria

a rational function W + U/V belongs to P if lc(W) > 0 or W = 0 AND lc(U) > 0

it follows that 1 - (anything/t) belongs to P and therefore anything positive/t is less than 1

I think that makes sense now, is my reasoning correct? anyway thanks

>>8621409
how about
u =y' and x = y

then

u'= sint - x
x'= u

??

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>>8617749

How do you do trig in 3d

I'm adding refraction to a ray tracer and I need to do this

>>8621487
thank you very much!

>23 years old
I'm looking to get a bs in EE, I'm studied in math up to Calc I, but aside from further calc, what could I self study with to prep for electronics courses when I can eventually transfer?

>>8621563
The only thing I remember is that the squares of the cosines in each plane should add up to one

i am supposed to find the supremum of the following set
[math]A=\{\frac{n+1}{n}\mid n\in\mathbb{N}\}[/math]
i know the answer is 2 but i don't understand the set notation. I gather A the set of values of [math]\frac{n+1}{n}[/math] where n is a natural number, but why?
shouldn't it be a subset of natural numbers where the property n+1/n is true, or even a set of boolean values depending on whether n+1/n is true for n.
sorry if this doesn't come off clearly, i'm really not sure how else to put it

>>8621709
>shouldn't it be a subset of natural numbers where the property n+1/n is true
What does "(n+1)/n is true" even mean to you?
It's a number. It doesn't make any sense to say "5/4 is true".

The first half of set builder notation tells you what to do with the number, and the second half tells you what numbers to use.

So in this case what you do with the number is take (n+1)/n, and the numbers you use are those that satisfy n in N.

>>8621709
>this whole post
smdh

>>8621563
The incident and refracted rays lie in the same plane, so it's only 2D.

Given the incident ray I and the normal N, construct a basis Z=N, X=I×N, Y= Z×X. Then you can convert I to 2D, find R, convert back to 3D.

how to make myself less dumb

>>8621887

yes but what if that plane is some where between the axises in 3d space

what is this conversion to 2d you speak of called so I can learn how to do it

In finite state automata, what does the automata take as input?
Words or elements from a set?

>>8621933
Just look at the definitions.
Basically it's input are words. Those words are elements from a defined language (subset of kleene-star of a alphabet).

Just imagine the FSA as a machine you can feed words into step by step into. THE FSA accepts or declines it. If the word is in your language (word from a language) it accepts it and if it's not, it declines it.

It helped me to visualize it and just look at simple definitions

What are some no-no topics when speaking to a fellow student regularly over uni email?

>>8621974
Thanks.
Do words not necessarily have to be tuples then?

>>8621995
For staying off a watchlist or something?

Don't reference weapons or illegal drugs and you should be good

>>8622002
Depends. The empty string can be a word for example as well and is not a 'normal' tuple. It would be () but some authors use any greek symbol for that as placeholder.

Single strings are just 1-tuples, ... and so on. It really depends what your professor made a convention in your lecture. Some define words like (h,o,u,s,e), (b,o,o,k), (), (a) as example for words while some professor say it's not necessary to differ and say it's okay to remove the brackets and commas. But to answer shortly: In a sense they're ALWAYS tuples but can (!) be written without the conventional-way. So, it really depends.

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>>8621563
By using vectors and inner products, nignog. It's stupid easy once you get the hang of it.

>>8622018
Sweet. Been doing that, or not, rather.

What's a brainlet?

>>8622207
someone who's not smart, or by /sci/'s usage someone who has an iq under 140.

>>8622207
that face when we are all brainlets in the face of the immensity of existence
that feel when:
https://www.youtube.com/watch?v=uwmeH6Rnj2E

>>8621243
If all [math]a_i\neq 0[/math] and n is finite, we know it converges.

>>8622292
>finite sums converge
groundbreaking discovery

>>8622303
thanks i'm writing up the paper now

How diffirent would our life be if circles didn't exist

>>8622323
Fine because a megagon (1,000,000-gon) would still exist.

>>8622348
Well 0 can't exist if circles don't exist.

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>>8622323
limp bizkit woulndt be as popular

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>>8621639
Linear algebra for sure

>>8617749

I lost my fucking backpack with all my textbooks and I want to die

>>8621255
It really is this >>8621267
It can take a while though

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>>8622908
>he doesn't have a GPS chip sewn into his backpack

>>8617749
Hi /sci/. I'm taking a cellular/molecular biology class and the chemistry aspect of the course has me feeling autistic.

So I have 310.15R= 0.616. R is the gas constant, and 310.15 is the absolute temperature at 37 degrees Celsius (273.15 kelvins+37 degrees Celsius).

I'm new to chemistry, is there any reason why I can't just solve for R algebraically? No value for R is given in my textbook. Thanks ya'll

Why can't we describe faster-than-light travel? Wouldn't doing so just flip the space and time axis

>>8622939
Of course you can solve for R algebraically. You haven't really told us specifically what you're trying to do. Mind posting the actual question / hw problem?

If the gravity affecting an object changes significantly as it travels, (say if you through a ball high enough into the earths atmosphere for g to change) what would its path look like? I know it wouldn't be a parabola but I don't know how to approach this problem.

Sort of think i should post this on lit, but i hate that toxic wreck of a board, so please bear with me

I want to read Kant, but his own pieces are pretty damn though to read through. Is there some lower Kant-entry point or some other author that touches upon his views on a more bearable manner?

Thanks in advance, anons.

linear algebra:

"Determine if the columns span Rn"
Can I just solve the matrix (rref) and if there's a 0 row at the bottom, then it doesn't span?

>>8623163
yeah

Does an automaton that has i, j and k repetitions of its language need to specify epsilon?
So for instance if it's:
L = {a^i, b^j, c^k | i, j, k => 0}
and you give it the input
{a,a,c}
why would it not accept that? Is it because the epsilon isn't explicitly declared?

What formulae do I use to find the velocity of a mass on an oscillating spring at a certain displacement?

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>>8617749
I'm a freshman in uni. I recently switched from a meme degree to civil engineering. I'm very behind on math due to the poor quality of the public education system of the Deep South.

Am I being overly ambitious? The only math class I'm taking right now is pre-calc. I'm studying a few hours a day using khan academy and so far I'm making good progress, but I'm not sure how steep the learning curve is. My plan is to spend the rest of this semester and all of summer studying every day. If I stick to this, will I be adequately prepared by the start of my Fall semester?

>> 8621896
> what is this conversion to 2d you speak of called so I can learn how to do it
Because X=I×N, X.I=0. So calculating Ix=X.I, Iy=Y.I, Iz=Z.I will give you a 2D incidence vector <0,Iy,Iz>. You can then use the law of refraction to find the 2D refracted vector <0,Ry,Rz>, and the 3D refracted vector is Ry*Y+Rz*Z.

>>8623239
Conservation of energy. Potential energy = (1/2)*k*d^2 plus kinetic energy = (1/2)*m*v^2 remains constant (i.e. equal to the sum at t=0).

>>8623175
Wtf did i just read. a^0 = 1, yea, so aac belongs to that language.

>>8622939
R depends also on the units used, and you can find it all over the internet, but as >>8622985 said, what's the question?

How do I rotate something by (0, 90, 0) relative to itself when it's already rotated?
I'm trying to get something in 3D to point in the right direction.

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>>8623392
>>8622985
X and Y are the concentrations of the reactants, in moles/liter.

Delta G is the change in free energy in kilocalories per mole. R is the gas constant, and T is the absolute temperature.

The second term in the equation is the standard free energy change.

But as of right now, I'd be happy to just know how or if I can find R. An example says that when T=37 degrees Celsius, RT=0.616. So 310.15R=0.616.

I'd also love to hear any suggestions for online chemistry resources. Thanks guys.

what is the inverse z transform of z^2/(z-1/2)^2

I have two values, forming an element of a some given set.

x: between 800 and 1000
y. between 15.00 and 25.00

As x decreases, y increases (and vv.), but neither by constant or determinable amounts.

Here's some example data:

843, 22.44
907, 20.20
909, 20.88
911, 20.64
926, 20.25
942, 19.64
987, 17.14

The value of x as y changes is not determinable, and vv.

The idea is to find the pair which offer the highest of both over the given data i.e. which pair is the most optimal for both values x and y in the given set.

Could anyone point me in the right direction as to approaching finding the most optimal pair over a given dataset? What is this discipline of math called?

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Let [math]A[/math] and [math]B[/math] be countable sets

[math]A \cap B = \emptyset[/math]

Construct a bijection between [math]N[/math] and [math]A \cup B[/math]

Help me out here famalams

>>8623649
can you think of two countable sets that lie in the natural numbers?

>>8623651
Not him but I doubt the problem means "find two sets A and B". That would be too trivial. It probably means finding a general bijection that would work for any A and B.

>>8623651
Even integers, odd integers. A = {1}, B = {2}. Or any infinite number of other possibilities. But I don't see how this helps prove the general case.

>>8623647
Whilst not a math solution, I used a two y-axis graph and found the element with the smallest gap between the plots

>>8623661
>Even integers, odd integers

ding ding ding, now can you relate it back to the question?

>>8623649
Let [math] X = A \cup B [/math]
By the well-ordering theorem then there exists an order such that X is well ordered. Which means that every subset of X has a smallest element. Then consider the function

[math]F = \{ (x,y) \in X \times \mathbb{N} / [/math] x is the smallest element of [math] X - C [/math], applying our order, where [math]C[/math] is the set of elements of [math]X[/math] smaller then x and y is the | [math]C[/math] |th natural number [math] \} [/math]

It is a trivial answer but it always works.

>>8623671
Not beyond the way I've already done, i.e. it fulfills the criteria for A and B. For all I know, A and B could be noninteger rationals starting with 3 and 7 respectively.

Right now I'm looking at mapping AuB to N*N and proving N*N is countable.

>>8623686
Evens and odds are not the sets A and B

The hint is that splitting N into two countable sets (evens and odds) is probably helpful when you have to count two other sets

>>8623686
what does it mean for A or B to be countable?
the actual elements of A and B do not even need to be numbers

then what does it mean for the odd or even numbers to be countable?

Tao's Analysis Vol I and II vs Rudin's Principles of Mathematical Analysis. Which is better?

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hi /sci/, i'm looking at some basic solid state physics stuff and this quantum stuff confuses me a lot. we haven't really looked at perturbation theory in lectures yet and i ran across this in the textbook. can you explain in brainlet terms how this expression for the perturbation in energy is arrived at?

>>8623721
Are you reading this by yourself? Tao.

Rudin is an established classic but it's difficult for a lot of people to self-study from because of how terse and unhelpful it is.

Don't get too hung up on what you read though. It's more important that you read _something_. 95% of intro analysis books will get you to roughly the same place.

I read an article about potential avenues for development of better photovoltaic cells, and there was one thing, I can't remember what it was called, some sort of nanoparticle called a piroskovite, or a ploskovite, or some fucking shit word, and now I can't remember the word and I can't find the article and it's driving me FUCKING INSANE just trying to remember the word

Can anyone help me?

>>8623872
Perovskite?

>>8623925

YES, thank you anonymous

ε([a,b])

What the meaning of this ?

>>8624099
need more context

>>8624109
The functions f, f' ∈ ε([a,b])
Show than if we have f(t)= f'(t) for all t except a finish number, so a∫b f(t) dt = a∫b f'(t) dt

Is 9 [math]\equiv -1[/math] mod [math]4[/math] in the same way that 9 [math]\equiv 1[/math] mod [math]4[/math]?

so what's the meaning of a real in front of an interval ?

>>8622022
>>8621887
>>8621663

I thought about it more

I think I could do 2d trig in a 3d plane if I somehow make the X and Y coords scalars of two vectors in 3d

How would I calculate the line that is orthogonal to the normal and opposite of the incident ray so I can use this ray as the X coord?

In the picture it would be the boundary

>>8624137
no, 9 is equivalent 1 mod 4 since 9-1 is divisible by 4

9 is not equivalent to -1 mod 4 since 9-(-1)=10 is not divisible by 4

>>8623254
Bumping this question.

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>>8623720
>>8623719
>>8623686
>>8623681
>>8623671
>>8623661
>>8623653
>>8623651
>>8623649
why are you guys overcomplicating this so much

A and B are countable so there exists bijections f: N to A and g: N to B
so define a bijection h: N to A U B by h(n)=f([n+1]/2) if n is odd and h(n)=g(n/2) if n is even

h(1)=f(1)
h(2)=g(1)
h(3)=f(2)
h(4)=g(2)
h(5)=f(3)
h(6)=g(3)
...

>>8624274
I just wanted him to use the axiom of choice (mine is the answer using the well ordering theorem) so that his professor would give him an autistic rant about why the AC is satanic.

It is not often that you get the chance of helping and trolling at the same time.

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>>8624306
>It is not often that you get the chance of helping and trolling at the same time.
apply yourself

you can always both help and troll if your mindset is pointing in the right direction

I am attempting to learn python as a hobby and at this point I realize my math memory is quite poor for figuring for what I want to accomplish, so here I am asking.

I am looking at a dataset of prices and counting consecutive streaks of increases and decreases. What I want to figure out is that when it reaches a threshold streak of X, what the probability X+1 will continue in that direction.

After that is incorporated I want to investigate change in current price into account to see what the correlation is. I am lost as how to begin that process of showing the relevance of %change to whether the streak will continue or not.

I am looking into running regression analysis through python but I would like to have a better understanding of what the actual math formula or theory would be to achieve this.

>>8624313
(my math terminology is a real limiting factor, I'm sure this is easily answered if I find the appropriate terms to ask)
However, while searching and reading about confidence intervals regarding streaks I found this patent which is something that I can work towards implementing. Is there something simpler to get me going?
https://www.google.ch/patents/US20120254176

>>8624313

What kind of prices are you looking at? If it's stocks, the probabilities will be misleading since other people will be running a similar (but more sophisticated) analysis to you, and buying and selling accordingly in order to maximize their profit. That will tend to dissipate any pattern your program might notice.

>>8624274
wanted to really make him think

& didnt want to do his homework 2bh

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Are semi-aquatic octopi plausible, given the correct environmental needs (brackish water, humid climate, lack of land predators, etc)?

>>8624341
It's currency prices. I realize that there is going to be more sophisticated black boxes doing this, I'm just trying to invest some time into building my own basic model so I can get somewhere more advanced later.

>>8623394
bump

>>8624372
Not really; what would they eat?

>>8624381

Look at all the past times there was an X-day long streak, and look at the distribution of how many times it continued vs how many times it didn't. That's your sample. Naively you can just use your sample data to make the probability, but you'll need to adjust for the fact that it's a sample and not the true distribution (look up sample mean vs true mean). If you really want to get serious you could look up maximum-likelihood estimation techniques.

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>>8624404
Most likely swamp insects, crustaceans, and any other small creatures that could live in a brackish swamp.

I have a discrete, uniformly distributed sample.

Say bunch of random numbers between 31 and 66.

How do I estimate the lower bound? All the literature I can find just estimates the maximum assuming it's a U(0,N) distribution, which is obviously not with such a high minimum in my case.

>>8617749
What is the specific heat capacity and heat of fusion for lithium 6. I am not interested in natural lithium or lithium 7. Also the value is different for lithium 6 and 7 just like the values of hydrogen and deuterium differ. This difference is not just seen when measuring based on mass vs moles, the values are actually truly different. Lithium 6 has a higher heat capacity but I would like to know how much higher.

Quick stupid question here.


25 lb @ 5 mph with surface area of 16 sqft
vs
2.5 lb @ 50 mph with surface area of 4 sqft

force applied to an object of 2 sqft n mass of 0.25 lb

Which would net greater force on the object?

>>8624614
force can't be calculated without knowing how quickly the momentum is exchanged. Area isn't used in force calculation, it's used for pressure

basically it's
momentum = speed * mass
force = momentum / time
pressure = force / area

>>8624446
Thanks this is a technique I was hoping to learn about. There's enough on stack overflow to go from here. Thanks again anon.

On my birthday, is the planet in the same place it was, the year before, in relation to the sun?

Can someone give me a hint as to how to start this? For the first part, I know that the green function is discontinuous at [math]x_{0}[/math], but is [math]x_{0}[/math] supposed to be [math]x'[/math]?

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>>8624822
Forgot the picture like an idiot

>>8624614
>>8624714

[math]D=1/2 \rho v^2 C_D A[/math]
[math]D_{25}=1/2 \rho (5^2) C_D (16)[/math]
[math]D_{25}=200 \rho C_D[/math]
[math]D_{2.5}=5000 \rho C_D[/math]

The third case doesn't make any sense but assuming the coefficients of drag are the same for the two bodies, the 2.5 lb object would have the greater force applied.

>>8624807
Of course it because we live in a geocentric universe.

Man I just don't fucking understand probability. Is there a no bullshit series on how it works other than rote memorization of problem solving strategies?

If we find out that a linear system is dependent, how do we know which vector to eliminate to make it independent? (without using determinant, cross product,)

>>8624841
He said in relation to the sun mate.

>>8624884
The Earth is flat and stationary and the sun and moon move above and around us.

>>8624931
Are you fucking serious? Stationary to the centre of the universe? Galaxy? Can't believe that. Fucking mental.

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>>8624259
No, just use 3D vectors from the start. Here, let me show you:

Let [math] \hat{v}_i [/math] be a (normalized) vector pointing in the direction of ray propagation and be incident on a surface.

Consider at the point of ray-surface intersection the normal to the surface [math]\hat{n}[/math].

To find the angle of incidence, use the dot product:

[math]\vec{a}\cdot\vec{b}=|\vec{a}||\vec{b}|cos(\theta)[/math]

[math]- \hat{v}_i \cdot \hat{n} = |1||1|cos(\theta_i) \Rightarrow \theta_i = cos^{-1} (-\hat{v}_i\cdot\hat{n})[/math]

Use the incident vector [math]\hat{v}_i[/math] and the surface normal [math]\hat{n}[/math] to construct a 3D basis using Graham-Schmidt orthonormalization and [math]\hat{v}_i \times \hat{n}[/math] as a third vector. In the special case where [math]\hat{v}_i[/math] and [math]\hat{n}[/math] are colinear (cross product = 0), then you don't have to worry about refraction since your angle of incidence [math]\theta_i[/math] is 0 (unless you are modeling anisotropic materials and their birefringence!)

USE VECTORS. THE MATH BECOMES STUPID EASY WHEN YOU GET THE HANG OF IT.

Ask if anything doesn't make sense, or if you have questions on how to use vectors to implement a ray tracer.

>>8623394
Bump 2
Electric Boogaloo

What are the effects of drinking coke with coffee? A friend warned me not to do it, and I have an increased arrhythmia risk so I don't want to try it just like that

Anybody heard of the CASPer test? I have to write it later today. It's just a generic morals/reasoning/writing test to weed out retards. It shouldn't be too hard but I'd like to get some practice anyways. Anybody know how I can prepare for this type of test? I want to sound eloquent.

Does watching anime makes you intelligent or being intelligent increases your tendenct to watch anime?? Why are there so many mathfag here posting chinese cartoons

>>8625713
They're making you [math]write[/math] the test? Can't help you there.

>>8625906
It's just entertaining. What should smart people do, only read Machiavelli and listen to classical music?

>>8625906
>Does watching anime makes you intelligent

God no

>being intelligent increases your tendency to watch anime

There might be a correlation here since it takes some level of intelligence to be introduced to anime, but it's probably not significant enough to prove.

>Why are there so many mathfag here posting chinese cartoons

cause this is a korean basketweaving site, you are more likely to see someone come to this board and post on it from one of the other anime oriented boards than to come from somewhere else on the web. Also a poster who is not interested in anime might mimic some of the other posters or boards. Overall I'd say that there isn't a lot of anime type posts on this board considering all of these factors.

>>8625925
Sorry, write as in type.

>>8622961
>Why can't we describe faster-than-light travel?

Because the current mathematical model used to describe such things starts spitting out infinities if you do.

>Wouldn't doing so just flip the space and time axis

Time really shouldn't be graphed that way.

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>>8625969
>it takes some level of intelligence to be introduced to anime

i know this is b8 but top lel

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How does this hold? a,b are elements of a group, btw.

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pls send help.. the lecture notes are utter shite

>>8625906
Anime, like all forms of escapism, appeals most to people who are unhappy with themselves and the world around them. Fantastic universes offer an alternative to the reality in which one is unattractive/socially inept/undervalued/incapable.

Naturally, that's a lot of /sci/.

>>8626009

a inverse cancels out the first a, so the sequence starts bababa.....b and ends with the extra a.

>>8626062
christ I'm retarded

thanks m8

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guys halp, is there even an answer to this?

>>8625906
>Why are there so many mathfag here posting chinese cartoons
There aren't really. I remember one guy who avatarfagged with them for like 2 months I suppose. The reason you see a lot of anime faces on /sci/ is because smug anime girls are really great for shitposting.

>>8626198
rephrase the question as an if and only if statement

>>8626245

x barber, y person

x shaves y, iff y does not shave themselves

use proof by case, since we are dealing with boolean:

if x exist, then....what? if x exist it does not imply that there exists a relation (x,y). it might be that a barber exist, but he never shave anyone.

if it x does not exist, who the fuck cares

>>8626262

extended rant: in the original paradox the issue arise with the statement (does the barber shave himself) because it forces the barber to contradict his "property" but if this is not enforced, the barber has no problem existing.

Is there any way to calculate how much mass object x needs in order for its gravity to affect object y at a distance of z? E.g. let's say I weight 80 kg, how much mass would an object at a distance of 1 m need in order for me to actually feel its gravitational pull?

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I dont understand the first part the vertex set thing can someone explain what it means?

I'm an undergraduate chemist with a comp sci degree, I've been racking my brain trying to come up with a product I can produce as a hobby. I am envious of other professions who create saleable goods. However, I'm not willing to produce illegal substances.

Any thoughts? I don't have enough waking-hours time to pick up more classes or work hours.

>>8626313
there are 8 elements in {0,1}^3

figure out what they are, then draw 8 points and label them

i assume you have the definitions of edge, component, degree and euler circuit

>>8626363
so what i just draw 8 points
can you tell me how/why that is?
yeah i know the definitions of the rest

>>8626391
there are 8 elements in {0,1}^3
figure out what they are

{0,1}^n is a subset of the R^n if that helps you think about this example

>>8626418
ok i kinda got it. I did the first {0,1} x {0,1}
now on the second multiplication should the elements still be 2 like ((0,0),0) would be the first or (0,0,0)
i only dealt with 1 edge for 2 vertexes how do i deal with 3 vertexes?

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>>8626430
>multiplication

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> verify that Q is consistent with all the R axioms except for completeness
WTF am I supposed to do?!

>>8626580
well what are the R axioms?

>>8626586
Addition and multiplication shit, connection of + and *, order shit and completeness. And it's like well + and * are defined on Q, so of course the fucking axioms check out. Order - yeah it's fucking ordered. Like what do they want?

>>8626613
>except for completeness
so show Q isn't complete

>>8626580

Remember: as long as it contains "verify" it's not a real problem. You can just skip it, I think it's intended for autists (why THE FUCK is this not a word?).

>>8626615
That's not what is fucking asked of me. Besides, how? You can always go one digit further to get your middle number.

>>8626629
is english not your first language? you literally wrote:
> verify that Q is consistent with all the R axioms except for completeness
this means you have to show Q is inconsistent with the completeness axiom

>You can always go one digit further to get your middle number.
literally what?

>>8626644
No it fucking doesn't. Even I show that Q is inconsistent with completeness I still have to show that it's CONSISTENT with all the others. BUT HOW FFS?!

Let's say we have 2.7868978907908908098 and 2.7868978907908908099 so what we do is we take 2.7868978907908908098.1 and there's the middle number. And even if they are infinite, 2.666777(5) and 2.666777(6) we just take 2.6667775.6 and there you go. So as you can see there can be no "show".

>>8626663
I need help.

>>8626663
you seem like a total brainlet, especially since you dont seem to even know what completeness means

>>8626674
I know what it fucking means. Means you got 2 reals and there'll be a real in-between them. So maybe shut the fuck up retard.

>>8626644

what he meant is that we can always "enhance" our rational number further and further to achieve a real number.

which is of course the definition of a real number.

>>8626678
>>8626678
>completeness means you got 2 reals and there'll be a real in-between them.
wrong again brainlet (and obviously wrong, since Q obviously satisfies that and you're being asked to show it doesn't)

feel free to read https://en.wikipedia.org/wiki/Completeness_of_the_real_numbers

>>8626690
>>8626690
>what he meant is that we can always "enhance" our rational number further and further to achieve a real number.
yes, and most real numbers aren't rational, which is what the point of this is, you can converge to irrationals using rationals

>>8626678

you are correct, rational number seems to be complete because for any x,y E Q we can always take ((x + y) / 2) E Q. So Q seems complete because we can do this infinitely many times so improve our number's accuracy.

iirc the definition of a real number is exactly this, we are taking a binary function f(n) with n->inf that maps Q to R by generating a sequence of number (f(1),f(2),f(3),...). As n-> inf we will approach that exact real number that we want.

I am not sure how to exactly answer that question.

>>8626705
stop misleading him brainlet

>>8626698
It's not fucking wrong you moron. Is this >>8626705 you? Cause if not you should apologize and admit my ultimate righteousness.

>>8626732
it is wrong brainlet, and that post is not me

as the wiki page describes (and which is consistent with the question you're being asked), you don't know what completeness is

>>8626739
I'm quoting from my FUCKING TEXTBOOK

> FOR ANY X AND Y there'll be some c SUCH THAT X <= C <= Y

Obviously it's something to do with the irrationals being dotted out and rationals BEING ABLE to actually approach them "after infinity", but how the fuck do you prove this?
But of course continue to believe your faggy wiki which doesn't even contradict this, it just says there are DIFFERENT FUCKING FORMS of the axiom.

I don't really know much about calculators. I need a calculator that can solve quadratic equations. I've always used wolframalpha for homework. Is there a calculator that acts like wolframalpha, where I can just enter the equation in any form and solve for x? Preferably something from amazon.

I'll be needing to solve some quadratic equations on an upcoming exam, I don't really want to waste time using the formula.

>>8626765
Just use fucking wolframalpha wtf are you autistic? Or are you a poor cunt who doesn't have THE PHONE WITH A FUCKING INTERNET connection? Either way stfu it's not your personal blog.

>>8626761
>>8626761
>> FOR ANY X AND Y there'll be some c SUCH THAT X <= C <= Y
your textbook is shit since you can trivially take C=X, please tell me what book this is so i can make sure no one reads it

and no brainlet, this doesn't contradict the wiki since all of the ones on the wiki page are equivalent and even the first description of completeness explicitly says why Q isn't complete
https://en.wikipedia.org/wiki/Completeness_of_the_real_numbers#Least_upper_bound_property

Give examples of quantities that possess both magnitude and direction.

Discuss the relation between a two-dimensional vector and a point in the plane. Discuss the relationship between a three-dimensional vector and a point in space.

How do the dot product and the cross product resemble (or differ from) the ordinary product of two numbers?

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Alright here is a stupid one. What happens to ashes ? How is ash transformed into anything? When we burn x grams of something do we permanently create x grams of useless dust or is it a part of something like nitrogen cycle?

>>8626805
>>8626810
>>8626815
same dude?

>>8626887
obviously

and obviously 3 homework questions

>>8626789
It's slightly different. X and Y are non-empty sets where every x is <= to every y. So there'll be a c such that x for every x and y x <= c <= y.

>>8626890
Homework questions are annoying, but their existence means that their professors have failed them.
If they've come to 4chan, that means that not only have their professors failed to teach them the information directly, their professors have failed to teach them the information in such a way that they can research it themselves if they misunderstand it.

I, for one, have no clue how you'd answer anything but the first question, they're rather strange questions to ask.
And the first question is extremely easy to answer if you have the slightest idea of what a vector would be used for; which means that the professor is so bad at teaching, that they didn't even give examples on how vectors would be used in the first lesson on the topic.

Shit like this is why I'm working on an educational AI as soon as the funding is available, math professors are worthless garbage most of the time in my experience.

>>8626937
you're excluding the possibility of a lazy brainlet student who doesn't go to class

>>8626937
No it fucking doesn't. It means they are useless lazy pieces of shit. The first question is 555-come-on-now tier. Stop blaming fucking teachers and shit, grow the fuck up faggot. Are you from Sweden? Go save a woman by getting raped instead of her.

>>8626943
>>8626937
especially when the person posting their homework here just pastes the question in and shows 0 evidence of having actually put in any effort (i.e. they don't say that they're stuck in any particular place)

>>8626921
then let X be the rational numbers less than sqrt(2) and Y the rational numbers greater than sqrt(2)

there's no such c so Q is incomplete

>>8626955
Oh yeah that's right thanks. But this was in the fucking textbook earlier, so clearly that's not what they want.

How DO I "verify" that other axioms apply?

>>8626943
If both the professor and the university are competent, the easy questions wouldn't even require going to class, because the notes would already be available.

Although going to class is a great idea if the professor is competent.

>>8626949
>teachers are blameless
It's rare that a teacher explains something in a way that I wouldn't be able to explain better myself, once I have proper understanding of it.
>in first university physics class, ask tutor why you can't use light from the sun to heat up something hotter than the sun
>long discussion where they constantly contradict themselves, and attempt an answer that makes up new laws of physics
>in my own time afterwards, work out that it's just basic optics, and figure out some very simple relationships that explain why sunlight can't heat something up hotter than the sun

>>8626952
You do realise that those questions are conceptual and not mathematical, right?
If you're stuck on them, you're not stuck at a particular step, you're stuck absolutely.

>>8626973
>>8626973
>so clearly that's not what they want.
this is exactly what they want

>How DO I "verify" that other axioms apply?
most of them are immediately inherited, aside from a few you need to check like multiplicative inverse (i.e. saying that if x is rational then 1/x is rational), mention that additive identity 0 and multiplicative identity 1 are both rational... it's not suppose to be complicated, the main point is the non-completeness

>>8626991
>If both the professor and the university are competent, the easy questions wouldn't even require going to class, because the notes would already be available.
there's 1000 textbooks on linear algebra, there's no reason to need your professor to post a pdf

>>8626991
>You do realise that those questions are conceptual and not mathematical, right?
how are you distinguishing 'conceptual' from 'mathematical'? regardless, there's still obviously been 0 effort put in

can the earth fall down?
is the universe something like a cube, with gravity holding earth in the middle somewhere?

If dna codes for proteins, where does the information required for the plasma membrane and lipids in general come from? I can ask a more specific question depending on your (eventual) answer.

>>8627014
The distinction is that conceptual doesn't require any usage or analysis of maths, but it requires you to understand the mathematical concepts.

Also, it's not like someone teaching maths suddenly becomes competent when they're writing a book.
They've got more time to work on their wording, sure, but the lack of the real-time feedback that comes with profession means that they can often have missing or even false information.
The textbook on linear algebra my university recommended was so full of missing information that there were huge jumps in the first few pages, so very soon it was explaining something that a first-timer would have no chance of understanding.
And that was just it attempting to explain what linear algebra was for.
Thank goodness for the internet which makes it quick to find good quality information by sheer numbers of things you can look at!

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>>8625055

So what exactly is graham schmitt orthonomralization?

I haven't really tried to understand the process because I don't understand the goal

>>8627106
>So what exactly is graham schmitt orthonomralization?
its an algorithm for producing an orthonormal basis from a given basis

it does this by subtracting off from a vector the 'common components' it shares with the previous vectors

>>8627117

And is a basis some vectors that represent axes?

>>8627168
basically yes

The atomic mass unit is defined as 1/12 the mass of an atom of carbon-12, right? So why is the mass of each nuclear particle sightly higher than 1 amu? Shouldn't the six neutrons and six protons add up to more than 12?

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>when you're at 79% in an online class and the professor won't give you that 1%.

Hello, I am in first week of Differential Equations and am stumped on the Algebra needed to isolate x in the equation:

[eqn].5*e^{2x}(x-.5) = -e^{-t}(t + 1) + C
[/eqn]

I honestly have no idea how to isolate the x in this equation so would be nice if can get steps.

Why doesn't interphase occur before prophase II?

Why doesn't latex work for me on sci anymore? Example:
[math] \mathbb{R} [\math]
[math]
\begin{bmatrix}
1 & 2 \\
1 & 3
\end{bmatrix} [\math]
[math] a^b [\math]

>>8627677
Flip your tag slashes

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>Serre will die in your lifetime

>>8627447
iirc protons and neutrons lose some mass when forming a nucleus because they are more stable.

>>8618052
about 7
all male obviously

>>8627447
That's the whole point. Mass and energy are, to some level, interchangeable. When protons and neutrons form bonds, they release energy. That energy comes from loss of mass, with the relation ΔE=Δmc^2. You'll notice the mass of nucleons in atoms heavier than iron rises - that's because iron has the lowest bonding energy, it is more stable.

>>8617794
>groups
Thank fuck I was allowed to work alone in college.

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>>8627559
hey one of you math boys help pls

>>8628268
It can't be done without resorting to esoteric functions. Leave it as an implicit solution.

>>8627106
The goal is to find a set of mutually orthogonal unit vectors that span the same space as the vectors you start with.

>>8626020
"sensitivity" is maximized when window duration is infinite. Specificity will go to hell, but that's not the question being asked. Your prof is a moron.

>>8624518
if you know the domain of the distribution, you can subtract a constant to map it onto [0,N]

>>8627854
>>8628018
Thanks anonymouses.

>>8618421
wise suggestion

Why are trig identities so fucking painful

I know nothing about meteorology but for a project I need to use some sort of system which could help me telling the weather in a specific area. I've found schematics to build some arduino things that detect air pressure, would this be enough to calculate weather patterns? what other data would i need them to gather?

How to score all A's in a semester? Give me some graceful tips.

>>8628874
Read your entire textbook (and make sure you understand every section) and do every exercise.

>>8628874
>>8628923
Doing the exercises is the most important part. Do every problem that is assigned to you, preferably without looking at your notes more than the first few times.

Ultimately what you're being tested on is your ability to do the problems, so if you want a good grade that's what you need to practice

>>8628923
>>8628927
what about courses such as biology our questions are more like what xxxx function etc...

So uh, I have a grad school internship coming up. Anyone have any advice about how to do well beyond reviewing the things I talked about in my statement and generally trying not to be a retard ?

>>8628969
>internship
Shit, I meant "interview", it's starting already

What's the general definition of 'formal' in mathematics?
Like if something is 'formal', what does that mean?

>>8629002
you mean like a formal proof?
https://en.wikipedia.org/wiki/Formal_proof

>>8629005
Well I'm studying formal languages, and I'm not entirely sure what makes them different from any other kind of natural language.
Like obviously they weren't formed by humans over time, but what makes them formal?

>>8629002
I'm not sure you should think too much about this. Just think of it as just one word.
Similarly, we talk about vector spaces, topological spaces etc . but the word "space" doesn't have a general definition

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I don't get the part about the total initial velocity.
Is the sum supposed to be magnitude of each term or something? I don't get either how to get the signs for each one.

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How would I answer the second part of this question? I think I understand what's going on, but I'm not sure how I'd prove that there's infinitely many such x.

>>8629186
The condition that xf=1 only constrains the values of x on U. Then, you can make it do whatever you want on W, which is infinite-dimensional.

>>8629228
Ah, I see. Thanks a lot

I want to create a program that reads TeX and basically creates an equation type/object from it. it will only support simplish algebra so it won't be hard. From there I might make it able to find solutions to diophantine equations.

I've learned from my past mistake of writing a PNG file reader in Python. Precision protocol shit is no fun in a scripting language. Plus the PNG file format has a library called libPNG which is really the only thing you should ever use to read a PNG file.

Does TeX have a version of LibPNG to do what am about to do?

>>8617794
kill your lab group

>>8618439
try this http://www.1728.org/angsize.htm

I'm stuck on a partial fraction decomposition problem from a calc text book

[math]\int{\frac{2x^3-4x-8}{(x^2-x)(x^2+4)}}[/math]

the book sets it up like this:

[math]\frac{A}{x}+\frac{B}{x-1}+\frac{Cx+D}{x^2+4}[/math]

Why the [math]Cx+D[/math] and not just [math]C[/math] over [math]x^2+4[/math]

something to do with it being a quadratic?

>>8629336
Cause the numerator will be x * (x - 1) * (C) which doesn't have the x^3 term in it.

What does this mean in English?

(∃x)(∀y)

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I know how to get the eigenvalues of a 3x3 matrix but how exactly can I tell which one has multiplicity? I mean, the matrix of my pic has the -3 and 5 as values but how can I do to know which one has multiplicity 2?

>>8629385
there exists x such that for all y

>>8629477
are you talking geometric multiplicity (dimension of the eigenspace) or algebraic multiplicity (multiplicity of root in the characteristic polynomial)?

>>8617749
just saying, i drew that image a long time ago (6-8 months?)
it is the only image i have ever drawn and posted
thanks for using it, it cleared my mood somehow

Where can I find carbon emissions per country for the years 2015 and 2016? All the information I find about carbon emissions stops at 2014.

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Who are these guys and why are they a meme?

>>8629520
Algebraic

>>8629591
well how did you find -3 and 5 as eigenvalues? presumably by computing the characteristic polynomial, you just read off the multiplicity of the root once you've factored the polynomial

>>8629384

So every fraction needs to have a polynominal of the same degree with the same powers?

>>8629627

in the numerator that is

>>8629048
bump
>>8629015
The use of formal logic

>>8629544
Why do graphs for current years take so long to release? Surely it doesn't take 2+ years to confirm the data?

Hoe do i solve

t * 1/(t^3)

It takes about an hour for me to go through 5~7 pages of this advanced linear algebra book, when they want to proof stuff about matrices.

Am i a brainlet or should i give up before i waste more time. I liked reading it.

Good stoichiometry learning guide?