Titles = {"sqt", "qtddtot"}

[Anonymous No.10913113]

Stupid Questions General.

>Sticky
https://sites.google.com/site/scienceandmathguide/

>Wiki
https://4chan-science.fandom.com/wiki//sci/_Wiki

Old thread: >>10887363

[Anonymous No.10913175]

Unsanswered questions:
>>10889006
>>10890104 (Yukarihomo gave an explanation, but anon specifically asked for a resource, so it still goes here.)
>>10893942
>>10894410
>>10898650
>>10899434
>>10900268
>>10901429
>>10901477
>>10901280
>>10910803
>>10912919

Retarded questions (for completeness)
>>10892615
>>10893605
>>10895954
>>10898113
>>10900917
>>10901354
>>10906996
>>10909902

Muscle:
>>10908613

[Anonymous No.10913230]

>>10912919

it's asking you to derive E(|Y-E(Y)|^2) = E(Y^2) - E(Y)^2. so just expand and use linearity of expectation

E(Y^2+2YE(Y)-E(Y)^2) = E(Y^2) - 2E(Y)^2 +E(Y)^2 = E(Y^2) - E(Y)^2

[Anonymous No.10913308]

Acoustic impedance. Just let me see if I get this straight.

Three layers:
1) Material A | 2) Material B | 3) Material A

Materal A and B has different specific acoustic impedance, so that the reflection ratio is 99%.
At a straight angle: equal ratios of sound energy are transmitted and reflected when traveling from 1) to 2), and vice versa. 99% of the sound is reflected back to the material it came from, and 1% is transmitted through.
The reflected sound bounces back in the material it came from, and keeps bouncing around there until it is attenuated by either material resistance or transmissions out.
For each bounce (say in material A) the wave loses 1% of its energy by transmission to Material B alone.
The sound energy entering 2) is always less than or equal to 1% of the energy originally sent from layer 1).
Some energy is reflected back yet again from 2) to 1) as the wave bounces there.
When traveling from layer 2) to 3), the process is repeated again.
The resulting transferred energy from layer 1) to layer 3) is equal to or less than 0.01%.
Does this also happen in practice, say, in buildings? Is it completely meaningless to assume a straight angle for sound transfer in natural milieus?

[Anonymous No.10913409]

https://www.cambridge.org/core/books/quantum-theory-of-fields/22986119910BF6A2EFE42684801A3BDF
https://arxiv.org/abs/1105.5289v3
https://www.worldscientific.com/worldscibooks/10.1142/3708

[Anonymous No.10913516]

>>10913230
kek, I was thinking it was asking for a derivative

[Anonymous No.10913621]

Where can I find the solutions book to Townsend's A modern approach to quantum mechanics?

[Anonymous No.10913629]

>>10913113
>json

disgusting. sql or gtfo.

[Anonymous No.10913643]

>>10913629
>json
Never used it but okay.

[Anonymous No.10913715]

Where can I find
>Introducing Pure Mathematics Smedley, Wiseman
>Understanding Pure Mathematics - Sadler, Thorning
not finding anything on google, yandex, duck, libgen, ebookee.
where should I look for math books? yes, I've read the sticky

[Anonymous No.10913756]

>>10913715
try private book trackers like bibliotik
look for some anon in the /ptg/ thread on /g/ to help you out.
warning most of the people in the thread are teenagers

[Anonymous No.10913876]

>>10911940
>>10912204
accidently asked this last thread after moving, but why doesn't light appear slower if its from a lamp on a train going away?

[Anonymous No.10913917]

How do I tag unanswered retarded questions? I have iPad.

[Anonymous No.10913945]

How can I cope with the fact that reading books is very boring?

[Anonymous No.10914001]

>>10913945
You must increase stamina for boring. If you want to read more, do so while cooking and shitting. You can get strength training in a white church or from watching plants grow.

[Anonymous No.10914087]

>>10913876
To understand that, there are a few facts you have to accept first:
1. EM wave travels at [math]c = \frac{1]{\sqrt{\mu_0\epsilon_0}}[/math] in vacuum.
2. All physical processes should be Lorentz invariant (does not care about what reference frame you use).
3. Light is the free propagation of EM waves.
Using the free form of Maxewll's equations in the Lorentz gauge [math]d\ast A = 0[/math], we have [math]\square A = 0[/math] where [math]\square = d\delta + \delta d = \frac{1}{c^2}\partial_t^2 - \nabla^2[/math] is the Laplace operator on Minkowski space (d'Alembertian). This proves the first and third statement.
Second statement is a fundamental principle in physics, you'll just have to take it on faith.

Now think about what happens when a charged particle is moving (on a train, for instance) in the presence of a magnetic field [math]B_0[/math]. In the frame outside of the particle, the moving charge generates a magnetic field[math]B[/math], while in the frame of the particle no magnetic field is generated, but the moving background field[math]B_0[/math] will generate an electric field [math]E[/math]. The equivalence between these scenarios is the celebrated unification of electricity and magnetism.
Now if the speeds [math]c,c'[/math] for the propagation of these fields are different in different reference frames, then you'd end up with two distinct Maxwell's equations, which leads to two different Lorentz forces acting on the particle. This contradicts statement 2, as different forces give different trajectories for the particle, which cannot be achieved by merely a change in the reference frame. Hence [math]c=c'[/math], proving the Lorentz invariance of Maxwell's equations.

[Anonymous No.10914135]

How can I get a first-year research position seeing as I have no CV? Do I just shoot my shot, so to speak? It's in physics/astronomy, if it's relevant.

[Anonymous No.10914172]

Why do people think that physics lovers are very smart?

[Anonymous No.10914194]

>>10913876
The speed being constant for all observers is a postulate of special relativity and an experimental fact.

[Anonymous No.10914429]

Help a brainlet out.
Why is
> -1^4
different than
> (-1)^4
? First one is -1, second one is 1. But why? It's always the same number, negative 1.

[Anonymous No.10914453]

>>10914429
Ok /sci/ no problem I got it.
>-1^4
you do 1^4 first (1) and then minus so -1
I got it on my own.
Thanks for nothing.

[Anonymous No.10914556]

Why is creating an augmented matrix in latex so retarded?

[Anonymous No.10914584]

quick stupid Graph Theory question: is the trivial graph also simple? I'm asking cuz i need to know if i need to change the base case in an induction proof im doing from n=1 to n=0 if the trivial graph counts as a simple graph. Although after typing that, i feel as though it might be better to keep n=1 since n=0 verifies the trivial case lolol

[Anonymous No.10914653]

>>10914429
>>10914453
just to let you know why this makes sense, the negative sign on an arbitrary number is a shorthand for "-1 times" which by the order of operations takes place after exponentiation. just like how -(4 + 5) is -9, not 1.

[Anonymous No.10914890]

What's the correlation between height and weight? I can't find anything.
By this I mean, take two men with the exact same proportions everywhere, but one is 1.2x taller than the other. Does the weight increase linearly with linear increase in height or is it an exponential increase? I'd assume the latter but I can't find any data.

[Anonymous No.10914898]

I don't tag you but I agree with assuming.

[Anonymous No.10914975]

>>10913175
>>10898650
You can try to find it with Google using "filetype:pdf" or "filetype:ppt"

[Anonymous No.10915565]

I'm struggling with this:
Suppose [math]G[/math] is a finite group and [math]M[/math] is a [math]G[/math]-module. Let [math]\bar{N} \colon M_G \to M^G[/math] be the map induced by the norm map [math]N \colon M \to M, m \mapsto \sum \limits_{g \in G} gm[/math]. If [math]M[/math] is a projective [math]\mathbb{Z} G[/math]-module, then [math]\bar{N}[/math] is an isomorphism.

I know [math] |G|[/math] annihilates both the kernel and the cokernel of [math]\bar{N}[/math]. Also, that map is an isomorphism if the module is induced (Brown's book, so [math] \mathbb{Z}G \otimes A[/math] and not the Hom-thingy). I just haven't been able to figure out how to use either of those things here. Would it make sense to try approach it from the direction that [math]M[/math] is a direct summand of a free [math] \mathbb{Z}G[/math]-module [math]F[/math], and then tensor them both with the integers? I would then have stuff like [math] F \cong \sum\limits_{i \in \mathcal{I}} \mathbb{Z}G[/math], so [math] F \otimes \mathbb{Z} \cong \sum\limits_{i \in \mathcal{I}} (\mathbb{Z}G \otimes \mathbb{Z}) [/math] for which the induced norm would indeed be an isomorphism.

Please, don't blow up when I post you.

[Anonymous No.10915570]

>>10915565
check your post by pressing that tex button at the top right of the reply box
:)

[Anonymous No.10915575]

>>10915570
I do, but it occasionally annihilates itself regardless. I guess I'm not too smart a boy.

[Anonymous No.10915584]

>>10913756
cheers.

[Anonymous No.10916459]

Is it legit to define a function life f(g(x)) = g(3)?

[Anonymous No.10916638]

>>10916459
Yeah.
Haskell even lets you do it, just use
f = \g -> g 3

[Anonymous No.10916709]

Answer fuckers!
>>10913917
I am equipped to answer retarded questions but am just shy of retarded myself. I want to do my part.

[Anonymous No.10916749]

>>10916709
You copy and paste the quote from the post.

[Anonymous No.10916756]

>>10916749
Now, I know twice as much. Will they see a (You)?

[Anonymous No.10916759]

>>10916756
No, cross-thread links don't do that.

[Anonymous No.10916761]

>>10887363

Let me practice on this retard.

Yes.

[Anonymous No.10916766]

>>10916759
Ok cool bro. Thanks.

[Anonymous No.10916793]

Anonymous 08/17/19(Sat)14:00:07 No.10895954

You sould read "The Martian" dude. There's something like this in there. Seems insignificant, what you proposed unless you have something specific in mind.

[Anonymous No.10916797]

>>10916793
Looks like i fucked that one up. It had an image and I think that messed with me.

[Anonymous No.10916806]

>>10916797
yup you fucked it up you european retard

[Anonymous No.10916886]

So I have a problem I've already solved, but on my first attempt I had a bad intuition, and I can't figure out why it's wrong beyond "it got da wrong number."

The problem was to take the two equations on the left, and solve for the difference between X and Y. It's 6. But, my original path was to write a version of the second equation with X on one side, write another version with Y on one side, then plug them each separately into the first equation, for X^2 + (13/X)^2 = Y^2 + (13/Y)^2. Both sides are the same except one has X and one has Y.

For a minute I thought that meant X=Y, but that's wrong. Then I realized the squaring meant they could be negations of eachother, but there were more differences.

[Anonymous No.10916908]

>>10916886
Try graphing X^2 + (13/X)^2 on desmos.

[Anonymous No.10917021]

>>10916806
But I am an American retard. What were the false indications, so that I may correct them?

[Anonymous No.10917056]

Constructive analysis vs classical real analysis. Which is preferable? Why?

[Anonymous No.10917077]

>>10916759
Cross thread.

[Anonymous No.10917100]

>>10917021
oh I see what went wrong
I was trying to deduce your timezone

But when hovering over the links in this post >>10913175 it shows the times in EST.
Only when I actually go to one of those posts does it show the time in my timezone.
I assumed that when hovering over them it would just show the time in my timezone as well.
That's why I miscalculated your timezone.

[Anonymous No.10917700]

any kind anon who can prove this using projective geometry only? im too stupid to understand all the explanations on youtube

[Anonymous No.10918575]

I am a chemistry major, and I am having difficulty choosing between intermediate mechanics and probability & statistics as an elective course. Which should I take?

[Anonymous No.10918597]

>>10918575
Definitely Probability and Statistics. They are fundamental subjects that everyone with a science degree should know.
Mechanics is pretty useless for a chemist.

[Anonymous No.10918609]

I know its cyclic because [math]81=3^4[/math] but i dont know how to find the generator without just bashing my head into the wall by taking the powers of all the elements, is there a nice way to do this?

[Anonymous No.10918809]

>>10918609
>multiplicative group of units mod 81
I know what those individual words mean, but what the fuck.

[Anonymous No.10919082]

>>10915565
Please...

[Anonymous No.10919235]

>>10917100
I did not know enough to not know that stuff. I am learning much from you.

[Anonymous No.10920024]

>>10918809
https://en.wikipedia.org/wiki/Modular_arithmetic
https://en.wikipedia.org/wiki/Group_(mathematics)
https://en.wikipedia.org/wiki/Multiplicative_group_of_integers_modulo_n
https://en.wikipedia.org/wiki/Cyclic_group

[Anonymous No.10920392]

Why are there no more polymaths?

[Anonymous No.10920464]

>>10920392
math is a lot harder now
look at how much work it took to prove fermat's last theorem

[Anonymous No.10920877]

>>10915565
Shit is greek to me. In fact, I'm certain that I see some Greek here.

Why you faggots no help this dude?
>>10919082

[Anonymous No.10921026]

Is numpy good for writing programs for a numerical analysis class?

[Anonymous No.10921054]

Hello, /sci/, computer science fag here.
I'm looking for options for a masters, is there a masters o phd that studies generative algorithms or swarm intelligence or models of traffic? The latter I'm sure is part of a broader area of study, what is it called?

I cant find masters related to the first two fields, how should I search for that? Thanks

[Anonymous No.10921180]

Are there any textbooks that say, like
>100 pushups. This is left as an exercise for the reader.

[Anonymous No.10921202]

Can dogs be Jewish?

[Anonymous No.10921220]

>>10921202
Only cats can be jewish, sorry goy.

[Anonymous No.10921252]

Okay, so I cooked some spaghetti noodles. I had some black beans so, I threw those in. That part doesn't matter. Then I put a little "A1 sauce" in there.

My question is: How do I even begin the process of obtaining recognition and winning my Nobel prize?

[Anonymous No.10921335]

>>10921026
Maybe. NumPy is designed for APL-style (vectorised) code, which is very different from Fortran/C-style code (with explicit loops). If the teacher is used to the latter, they're likely to have trouble understanding the former.

[Anonymous No.10921369]

What note taking app should i use to take simple history/geology class notes? also what are some efficient note taking methods?

[Anonymous No.10921381]

>>10921202
No, dogs have buddha-nature.

[Anonymous No.10921382]

I think they still make paper.

[Anonymous No.10921652]

>>10921202
all dogs go to heaven, so therefore no dogs are jewish

[Anonymous No.10921656]

>>10921369
>>10921382
Is this your post, sir?

[Anonymous No.10921657]

I have been doing nothing but sit around watching youtube videos for the past 2 days, what the fuck is wrong with me? I know I have actual useful things I could be doing, but I can't bring myself to do anything like that, can't even bring myself to play video games anymore.

[Anonymous No.10921666]

>>10914172
I hate this

[Anonymous No.10922262]

There was an image that was comparing all the university majors or areas of study or something like that.
Y axis was Math
X asix was inteligence
red line going from 0,0 to top right
I am looking for this image
It had engineering at the top (high y), physics at top right (high x and high y) and linguistics at high x.
PLease does anyone have this image or know how I could find it.

[Anonymous No.10922265]

>>10921657

welcome to the ADD-with-comorbid-depression club.

[Anonymous No.10922459]

>>10918609
81 being a prime power is not sufficient to conclude that U(81) is cyclic (see U(8)). We know it's a group of order 54 by the Euler phi function, so there are only 3 possibilities for it. In this case, I think it does turn out to be cyclic; 2^27 is -1 mod 81, if my mental arithmetic is right.

>>10915565
What is [math]M_G[/math] and [math]M^G[/math] in your notation?

[Anonymous No.10922461]

>>10922459
Coinvariants and invariants, respectively.

[Anonymous No.10922651]

So I have this simple True RMS circuit. How do I calculate R and C to the given [math]U_{IN}[/math] so the [math]U_{OUT}[/math] is the average of the [math]U_{IN}[/math]?

[Anonymous No.10922671]

>>10922651
Isn't that just a lowpass filter to give the DC offset? Find the RC time constant for your lowest expected frequency

[Anonymous No.10922819]

How do I find <p^2>, if I'm given the wave function?

[Anonymous No.10923049]

Is it true that after 50 your mathematical ability goes to shit or was GH Hardy just projecting

[Anonymous No.10923148]

how bad of an idea is it to take diffeq and calc III in the same semester, but only those two classes

[Anonymous No.10923327]

>>10923148
Doesn't seem bad, neither of them is particularly problematic. If anything taking just two classes for the semester may be a bit of a waste if time, but if you are working or need time for something else then you're good.

[Anonymous No.10923442]

>>10923327
It's a backup in case I don't get accepted into the uni I'm trying to transfer to for the spring semester.
If I don't, those two classes are the last two classes I can take for my EE degree that are offered at my community college.

[Anonymous No.10923558]

How many hours a week should I reasonably study to understand Calculus II in two months if all I know is basic trig.

[Anonymous No.10923567]

>>10923558
You can do math good, but can't figure out that you just need to keep reading it until you understand it however long it takes?

[Anonymous No.10923587]

>>10922819
First let us identify what "[math]p[/math]" means. Under holomorphic quantization, we promote [math]f\in C^\infty(M)[/math] to linear operators [math]\hat{f} \in \operatorname{End}B[/math] on the prequantum Hermitian line bundle [math]B\rightarrow M[/math]. Now with the polarization [math]\{X_p\mid \qquad p = (0,p) \in M\}\subset TM[/math], we polarize out the momentum dependence on the operators [math]\hat{f}(p,q) \rightarrow \hat{f}(q)[/math]. In this way, the function [math]f(p,q) = p[/math] is promoted to the vector field [math]\hat{f}(q) = \partial_q[/math].
Now the Hermitian inner product [math]\langle \cdot,\cdot\rangle: B\times B \rightarrow \mathbb{C}[/math] allows us to form [math]\langle \cdot, \hat{f}\cdot\rangle: B \times (\operatorname{End}B \times B) \rightarrow B\times B \rightarrow \mathbb{C}[/math] on which [math]\operatorname{End}B[/math] acts on [math]B[/math] as usual. Hence given a section [math]\psi: M\rightarrow B[/math], we can form [math]\langle\psi_q,\hat{f}(q)\psi_q\rangle \in \mathbb{C}[/math] for each [math]q \in M[/math].
Let us denote the polarized manifold again by [math]M[/math]. Treat [math]\omega(q) = \langle \psi_q,\hat{f}(q)\psi_q\rangle d\operatorname{vol}\in\Omega^n(M)[/math] as a top form in [math]M[/math], where [math]d\operatorname{vol}[/math] is thevolume form and [math]\operatorname{dim}M = n[/math]. Then we may use the non-degenerate de Rham pairing to form
[eqn]\int_M \omega= \int_M \langle\psi_q,\hat{f}(q)\psi_q\rangle d\operatorname{vol} \equiv \langle \hat{f}\rangle.[/eqn] Put [math]\hat{f} = \hat{p}[/math] yields the result.

[Anonymous No.10923590]

>>10923587
Meant [math]\hat{f} = \hat{p}^2[/math].

[Anonymous No.10923595]

>>10923567
I need to take a Calc III class next semester bro

[Anonymous No.10923599]

>>10923595
Just do a chapter every 3 days or something?

[Anonymous No.10923620]

For tabular integration, when both the integral and derivative columns never approach 0, when do you know to stop integrating/differentiating?

[Anonymous No.10923797]

>>10922459
It is cyclic because group of units of odd prime powers are cyclic.

[Anonymous No.10923803]

>>10923558
30+ hours, its not that difficult use a good textbook you are comfy reading and make sure to do the more difficult end of chapter problems, don’t waste time grinding the early exercises just to boost confidence.

[Anonymous No.10923828]

>>10923620
You shouldn't be using tabular integration

[Anonymous No.10923924]

>>10923590
bruh how the fuck do i calculate (-i*h*d/dx)^2 of psi? Is it just -h^2 times the second derivative of psi? Or is it the first derivative of psi, squared?

[Anonymous No.10923938]

>>10923828
why shouldn't I be using tabular integration

[Anonymous No.10924010]

>>10913113
How is pi irrational if it's c/d? Something's fundamentally wrong here!

[Anonymous No.10924015]

>>10923803
>30+ hours a week
>already doing 10 hours of lectures and 30 hours of studying
oh boy, guess i have no choice tho

[Anonymous No.10924026]

So I'm in babby's first analysis class, and I can prove that, given natural numbers p, k, and n, if p is divisible by n, then [math]p^k[/math] is divisible by n; but I'm having trouble proving the converse.

I know that any natural number is composed of prime factors, so do I have to assume that n is prime in this case?

[Anonymous No.10924059]

>>10924015
just work through something like Apostol's Calculus at a steady pace throughout the term and then review over the break you should be fine. If you're taking classes this semester/quarter and have a lot on your hands don't study for Calc 30 hours a week that will not end well for you. Try not to think of it as a set amount of hours you need to accumulate just work on your intuition and problem solving techniques for the subject you will move faster this way while learning far more.

[Anonymous No.10924062]

>>10924026
It isn't true. 2 isn't divisible by 4 but 2^3 is.

[Anonymous No.10924070]

>>10923924
> (-i*h*d/dx)^2 of psi?
Meaningless. If you're trying to convert mathematical notation to ASCII; you screwed up; post a pic.

[Anonymous No.10924105]

>>10924062
4 isn't prime though

[Anonymous No.10924109]

>>10924105
Proof?

[Anonymous No.10924111]

>>10924109
2 * 2 = 4

[Anonymous No.10924323]

>>10924010
Find integers c and d such that pi = c/d.

[Anonymous No.10924345]

>>10924323
pi=pi^0/0^pi

[Anonymous No.10924349]

>>10924345
Nope π!=infinity

[Anonymous No.10924380]

If Voyager 1 is traveling at 17 km/s relative to the sun and the sun orbits the galaxy at a speed of around 200 km/s does that mean voyager 1 is traveling at a speed of 217 km/s relative to the galaxy? How does this work? Trying to wrap my head around it.

[Anonymous No.10924381]

>>10924349
every possible number is equal to infinity

[Anonymous No.10924458]

Does anyone have an alternative to textsheet?

[Anonymous No.10924485]

>>10924105
Who said anything about primes? It just says
> given natural numbers p, k, and n

As for
> so do I have to assume that n is prime in this case?
Clearly not for the forward case. p^k = p*p^(k-1), so if p is divisible by n then p=a*n and p^k=a*n*p^(k-1) which is divisible by n. This doesn't require either p, k or n to be prime. p^k is only prime if p is prime and k=1.

For the converse, if p^k is divisible by n then all of the primes which occur in the factorisation of n occur in the factorisation of p and thus of p^k. However, n may have one or more prime factors with an exponent greater than in p. E.g. if n=12=2^2*3^1 and p=6=2^1*3^1, p^k divides n for k>=2 but p doesn't. Even if p>n, it doesn't necessarily follow the p^k|n=>p|n. E.g. If n=12=2^2*3 and p=18=2*3^2, p^2 is divisible by n but p isn't.

If n is prime, then p^k is only divisible by n if the prime factors of p include n, in which case p is divisible by n. More generally, if n is square-free (i.e. its factorisation doesn't include squares of primes or higher powers of primes) then p^k is divisible by n iff p is divisible by n.

[Anonymous No.10924902]

>if you move a fluid around a perfect angle, the velocity becomes infinite
I don't get it. What's the probem here? Isn't a perfect right angle basically indifferentiable? At that point, wouldn't you have to model the flow around the bevel of an atom, or a grain of sand instead?
Why do mathfags always assume inifinitesimals are meaningful?

[Anonymous No.10924925]

Showing [math]a_n>0[/math] is simple enough, but im lost for actually showing the series is divergent. I've tried showing [math]lim(a_{n+1})/lim(a_n)\geq lim(1-1/(n+1))=1[/math], and from this getting [math]lim(a_{n+1})\geq lim(a_n)[/math], then since the terms are always positive you can deduce that [math]lim(a_n)\neq 0[/math], so the series doesnt converge, but that doesnt sit right
can anyone offer some clarity

[Anonymous No.10925350]

>>10924925
[eqn] \frac{a_{n+1}}{a_n} = 1 - \frac{1}{n+1} = \frac{n}{n+1} \\
a_n = a_1 \prod_{k=1}^{n-1} \frac{k}{k+1} = \frac{(n-1)!}{n!} a_1 = \frac{1}{n} a_1 \\
\sum_{n=1}^\infty a_n = \sum_{n=1}^\infty \frac{1}{n} a_1 = a_1 \sum_{n=1}^\infty \frac{1}{n}
[/eqn] which diverges

[Anonymous No.10925377]

>>10925350
Anon's problem says that it's greater than or equal to but this still works just use the comparison test.

[Anonymous No.10925384]

>>10925377
I know, but if it diverges when using the smallest ratio between terms then it obviously also diverges for larger ratios

[Anonymous No.10925676]

VERY IMPORTANT QUESTION PLEASE ANSWER

Say you have a smooth function from [math] \mathbb{R}^n [/math] to [math] \mathbb{R} [/math] that satisfies the following:
1) There exists a point [math] x_0 [/math] where the derivative (the Gradient) is zero.
2) The second derivative (the Hessian) is strictly positive definite at All the points in [math] \mathbb{R}^n [/math].

Do the above imply that f has exactly one extremum, a global minimum at [math] x_0 [/math]?

I am pretty sure that it holds for functions from R to R, but I am not sure about multivariable ones.

[Anonymous No.10925722]

T = 4
So I integrate t^3 from -2 to 2 , and it's multiplied by 1/4.
I'm getting some wonky number 9.142

Should also be multiplying it be the amplitude, which is 8?

Formula for power that I'm using is 1/T * integral of g^2(t) from T/2 to -T/2

[Anonymous No.10925728]

>>10913113
a lot of niggas gonna fail calculus on this board desu lol

[Anonymous No.10925736]

>>10925728
HELP ME 4CHAN WHY AM I SO BAD AT ANTIDERIVATIVES

[Anonymous No.10925777]

>>10925722
you got the correct answer, 64/7
doesn't matter if it's "wonky"

[Anonymous No.10925787]

>>10925777
So the amplitude doesn't matter when calculating the power of a signal?
Well, I guess it shouldn't because we're integrating that's where the period ends?

[Anonymous No.10925825]

>>10925787
yeah you don't have to do anything with the amplitude

[Anonymous No.10925840]

>>10924902
It sounds like you do get it?

[Anonymous No.10926025]

Can anyone help me out with this? It's with R.

[Anonymous No.10926670]

>>10925676
nvm found it
https://en.wikipedia.org/wiki/Convex_function#Functions_of_several_variables

[Anonymous No.10927293]

how would i go about calculating the radius of converge for this thing here? it almost seems like its a sequence of partial sums of partial sums, but im stumped

[Anonymous No.10927298]

>>10927293
retarded

[Anonymous No.10927393]

>>10925676
if there are two extrema, you can join them by a curve and investigate the function over this curve. if you know it's true for R -> R functions, you will get contradiction.

[Anonymous No.10927625]

>>10927293
>>10925722
The numerator is 2^n (n + 1)!
The denominator is bounded above and below by 3^n (n + 1)! and 3^n n! respectively.
Now you should be able to find the radius by applying the Cauchy-Hadamard theorem and the Stirling approximation.

[Anonymous No.10927785]

Can a big brain help me with pic related? I'm stuck on i) and generally have a poor understanding of problems where I need to prove or show something. Any hints & tips are all appreciated.

[Anonymous No.10927948]

>>10927785
[eqn]
\mathcal L \{f\}
= \int_0^\infty e^{-st} f(t)\,dt
= \int_0^T e^{-st} f(t)\,dt + \int_T^\infty e^{-st} f(t)\,dt
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-s(t+T)} f(t+T)\,dt
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-s(t+T)} f(t)\,dt
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-st}e^{-sT} f(t)\,dt
= \int_0^T e^{-st} f(t)\,dt + e^{-sT} \int_0^\infty e^{-st} f(t)\,dt
= \int_0^T e^{-st} f(t)\,dt + e^{-sT} L{f}
= \int_0^T e^{-st} f(t)\,dt + \mathcal L \{f\}
\Rightarrow (1-e^{-sT})\,\mathcal L \{f\} = \int_0^T e^{-st} f(t)\,dt
\Rightarrow \mathcal L \{f\} = {1 \over (1-e^{-sT})} \int_0^T e^{-st} f(t)\,dt
[/eqn]

[Anonymous No.10927960]

>>10927785
\mathcal L \{f\}\\
= \int_0^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_T^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-s(t+T)} f(t+T)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-s(t+T)} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-st}e^{-sT} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + e^{-sT} \int_0^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + e^{-sT} L{f}\\
= \int_0^T e^{-st} f(t)\,dt + \mathcal L \{f\}\\
\Rightarrow (1-e^{-sT})\,\mathcal L \{f\} = \int_0^T e^{-st} f(t)\,dt\\
\Rightarrow \mathcal L \{f\} = {1 \over (1-e^{-sT})} \int_0^T e^{-st} f(t)\,dt\\

[Anonymous No.10927965]

I want to understand matrix multiplication with vectors.
What is this thing in abstract algebra?
We are multiplying a matrix nxn by n-column vector to produce another vector. What set is this? Is this heterogeneous set of matrices and vectors?
But group theory says set G should be homogeneous. It doesn't explicitly say but it is implicitly assumed right?
Please someone explain what is this matrix transformation is in terms of abstract algebra

[Anonymous No.10927970]

>>10927785
[eqn]
\mathcal L \{f\}\\
= \int_0^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_T^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-s(t+T)} f(t+T)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-s(t+T)} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-st}e^{-sT} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + e^{-sT} \int_0^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + e^{-sT} L{f}\\
= \int_0^T e^{-st} f(t)\,dt + \mathcal L \{f\}\\
\Rightarrow (1-e^{-sT})\,\mathcal L \{f\} = \int_0^T e^{-st} f(t)\,dt\\
\Rightarrow \mathcal L \{f\} = {1 \over (1-e^{-sT})} \int_0^T e^{-st} f(t)\,dt\\
[/eqn]

[Anonymous No.10927981]

>>10927785
[eqn]
\mathcal L \{f\}\\
= \int_0^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_T^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-s(t+T)} f(t+T)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-s(t+T)} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + \int_0^\infty e^{-st}e^{-sT} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + e^{-sT} \int_0^\infty e^{-st} f(t)\,dt\\
= \int_0^T e^{-st} f(t)\,dt + e^{-sT} \mathcal L{f}\\
\Rightarrow (1-e^{-sT})\,\mathcal L \{f\} = \int_0^T e^{-st} f(t)\,dt\\
\Rightarrow \mathcal L \{f\} = {1 \over (1-e^{-sT})} \int_0^T e^{-st} f(t)\,dt\\
[/eqn]

[Anonymous No.10928008]

>>10927965
Look up vector spaces. Matrices are (a representation of) the homomorphisms between vector spaces.

[Anonymous No.10928046]

>>10927981
>>10927970
>>10927960
Thanks for posting, was very helpful to go through step by step

[Anonymous No.10928314]

>>10915565
AAAAAAAARGH

[Anonymous No.10928916]

What is the perfect definition of physics? How does one get into it as just a sort of hobby?

[Anonymous No.10929034]

>>10927625
How were you able to discern this? When I was attempting it I could tell that there was some way to write the parts in some factorial form but couldn't translate it

[Anonymous No.10929037]

>>10927625
How were you able to discern this? When I was attempting it I could tell that there was some way to write the parts in some factorial form but couldn't translate it

[Anonymous No.10929217]

>>10929034
Use the inequalities 3k < 3k + 1 < 3(k + 1) and take the product from k = 1 to n on all sides of the inequalities to get the bounds for the denominator. The numerator is just equal 2^n (n + 1)! as you can see by factoring out the 2 from each term. Also, you don't actually need the Stirling approximations because the factorials in the numerator and denominator cancel.

[Anonymous No.10929379]

>>10913113
I was watching a lesbian 3 way with 2 BBW (big black women) and 1 really tiny white teen where the tiny whitey got her face shoved into the other ladies butts, you know, as you do, when i instead realized i weren't even interested but instead closed my eyes and fantasized about something else more real.

Does this mean I'm cured of my porn addiction?

[Anonymous No.10929386]

>>10929379
Not science or math >>>/adv/

[Anonymous No.10929391]

What are +, -, ×, and ÷ called. Is there a single blanket term for them? Its been bothering me because they never told us but there definitely is a name for the four basic function signs right?

[Anonymous No.10929396]

>>10929391
elementary operations

[Anonymous No.10929669]

>>10928916
Predicting nature

[Anonymous No.10929835]

Could someone please give me a hint on how this would be done?
https://www.spoj.com/problems/KPPOLY/
All I need is a concept

[Anonymous No.10929883]

>>10929835
An extreme point is a point that cannot be written as a convex combination of two other points.

[Anonymous No.10929887]

Can someone explain this to me like I'm stupid? I fucking might be. I don't understand how the steps relate to the figure.

[Anonymous No.10930058]

>>10929883
Sorry, I can't see how that implies a solution

[Anonymous No.10930091]

>>10929883
>convex combination of two points
isn't that just the line segment between them?
It's even said that the polygon is convex and no three points on the input are on the same line

[Anonymous No.10930167]

>>10930058
The projection is always the difference between the extreme point furthest and the one nearest.

[Anonymous No.10930198]

>>10930167
stating the obvious here. are you sure you would be able to solve it? otherwise thanks for responding

[Anonymous No.10930335]

>>10929835
Trigonometry. Partition the range [0,2π) according to which vertices are the top, bottom, left, and right. For each interval, each projection is the peak of a sinusoid, and the sum of sinusoids is a sinusoid, the amplitude of which is the peak value for that interval. The minimum will occur at a boundary, when an edge is horizontal or vertical.

[Anonymous No.10930358]

Find all prime p for which p^2 divides 9^(p^2) + 1

I know I'm supposed to use euler's theorem somehow but I still can't solve the equation halp

[Anonymous No.10930396]

>>10930198
Take any two vertices (i.e. extreme points) and calculate their distance. Call it d1. Cycle through all choices of two other vertices that don't include the original two, take the difference vector, remove the projection onto the original difference vector, compute the norms of all of these vectors, and call it d2.
Maximise d1+d2 cycling through all initial vector choices.
Do some trickery to minimize workload (left to you as an exercise).

[Anonymous No.10930516]

>>10930396
Oh, right, d2 is the largest norm.

[Anonymous No.10930560]

>>10930396
might be good enough for maximization, but not minimization

[Anonymous No.10930609]

>>10930560
besides, someone in the comments wrote they have a O(n) solution. I can't believe that myself, but this n^4 solution doesn't seem anywhere near optimal

[Anonymous No.10930632]

>>10930560
Wait, minimization?
Huh, I thought it was maximization.
>O(n)
I wouldn't be surprised if you could optimize that into O(n). I pretty much wrote it in the single most wasteful way possible.

[Anonymous No.10930687]

>>10930632
>I thought it was maximization
It's both

I'm still withing for a non obvious answer

[Anonymous No.10930814]

>>10929887
this picture made me re evaluate my life. I used to be good at math, especially calculus. but reading this gave me a headache.
I'm going to go back to reading my old math books and see if my brain still works like it used to

[Anonymous No.10931034]

>>10930944
Show that f(x+nT)=f(x+(n+1)T)=f(x+nT+t) by setting a = nT and applying the definition, then you chain up equalities (by induction).

[Anonymous No.10931036]

>>10931034
My bad, a = x+nT.

[Anonymous No.10931321]

Hello everyone, I am creating a graph for a physics lab report. The title of the graph must be UNDER ten (10) words. This is the title I have so far: Motion of an Object With Initial Velocity Along a Horizontal. As you can see, this title is exactly ten (10) words. How should I shorten this title and maintain the idea expressed by the title? Thanks, and sorry for my autistic writing.

[Anonymous No.10931392]

>>10931321
>tfw 10 word graph title due in two weeks
How fucked am i /sci??

[Anonymous No.10931419]

>>10931321
Would "Object Motion With an Initial Velocity Along a Horizontal" suffice?

[Anonymous No.10931484]

>>10931321
>Motion of an Object With Initial Velocity Along a Horizontal
=>
>Object Motion With Initial Velocity Along a Horizontal

[Anonymous No.10931494]

>>10931321
horizontal motion of an object with initial velocity

[Anonymous No.10931593]

What is a good textbook/lecture notes about neural networks for mathematicians?

[Anonymous No.10931724]

>>10930814
I think it's a problem with the writing. There are other problems that I couldn't do because they were unclear.

I think I figured it out and the point he's trying to get at is that (c,C) and (c*,C*) are the same point, but I don't understand why he goes about it like that. I feel like it's pretty obvious that the mean value between two straight lines is a straight line halfway between them and so regardless of which mean you find first it will just be the point in the middle. The dotted lines also just added more confusion than clarity.

[Anonymous No.10931754]

>>10930609
> someone in the comments wrote they have a O(n) solution.
>>10930335
The number of intervals is equal to the number of edges. The angle where the left-most vertex changes from v_n to v_n+1 is when the edge between those two vertices is horizontal. Also note that the system has 90 degree rotational symmetry.

[Anonymous No.10931819]

>>10931724
>(c,C) and (c*,C*) are the same point
They most definitely are not. See below.
>regardless of which mean you find first it will just be the point in the middle
The mean value theorem says that if you have a function [math] g [/math] on an interval [math] [a, b] [/math] so that [math] g[/math] is continuous and differentiable there, then [math] g(b) - g(a) = g'(c)(b - a) [/math] for SOME point between a and b. Note that c is not guaranteed to be the mid-point of a and b. For example, take [math] g(x) = x^3 [/math] on the interval [math] [0, 1] [/math]. Then [math] g'(x) = 3x^2 [/math] and [math] g(1) - g(0) = 1^3 - 0^3 = 1 \neq g'(1/2)(1 - 0) = 3/4 [/math].

What the steps given in the picture do show is that [math] f_{xy}(c, C) = f_{yx}(c^*, C^*) [/math]. Observe that [math] (c, C), \ (c^*, C^*) [/math] depend on f, its derivatives and on the rectangle you're considering. You are asked to impose a condition on [math] f_{xy}, \ f_{yx} [/math] so that [math] f_{xy}(a, A) = f_{yx}(a, A) [/math] holds. As you shrink the rectangle towards the bottom left corner, [math] (c, C) \rightarrow (a, A) \leftarrow (c^*, C^*) [/math]. And [math] f_{xy}(c, C) = f_{yx}(c^*, C^*) [/math] for each of the rectangles you get as you approach the bottom-left corner. So [math] f_{xy}, \ f_{yx} [/math] approach the same value as [math] (c, C) \rightarrow (a, A) \leftarrow (c^*, C^*) [/math]. Furthermore, if [math] f_{xy}, \ f_{yx} [/math] are continuous, then [math] f_{xy}(c, C) \rightarrow f_{xy}(a, A) [/math] and [math] f_{yx}(a, A) \leftarrow f_{yx}(c^*, C^*) [/math]. But we just proved that these limits must be equal so [math] f_{xy}(a, A) = f_{yx}(a, A) [/math]. As [math] (a, A) [/math] was an arbitrary point of the domain, this shows that [math] f_{xy} = f_{yx} [/math] as functions. So the continuity of the second partial derivatives is sufficient to show that they must be equal.

[Anonymous No.10931918]

>>10931819
I think I was conflating the mean value theorem with the average value of a function. Thanks for explaining the proof.

[Anonymous No.10932363]

Why are math papers always written so dryly? They never sound happy that their arguments work.

[Anonymous No.10932389]

>>10932363
are you talking specifically about paper, or about math texts in general (textbooks, monographs) ?

[Anonymous No.10932412]

I'm sorry this is probably super easy, but I'm really hesitant, haven't done statistics in a very long time.

>3 dices
>pick one number (between 1 and 6) and bet 10 bucks
>if number appears on 3 dices, win 40 bucks
>if number on 2 dices, win 30 bucks
>if number on only one die, win 20 bucks
>what's the expected win or loss
My guess is that the answer is 20 * p(1 die) +30 *p(2 dices) + 40 * p (3 dices), but I feel like I'm missing something

[Anonymous No.10932424]

>>10932389
More about papers. In textbooks authors are more joyful from my experience.

[Anonymous No.10932429]

>>10932412
>but I feel like I'm missing something
yeah you're missing the "- 10 * p(0 dice)"

[Anonymous No.10932438]

>>10932412
there are 6^3 total possibilities.
1 is you winning 40
3*5 are winning 30
3*5^2 winning 20
and the rest is winning nothing
if you add that up you get an expected price of 1990/216, which is roughly 9.2, ie. if you play long enough you will lose 80cents for every game you played

[Anonymous No.10932514]

>>10931419
>>10931484
>>10931494
Thank you so much everyone.

[Anonymous No.10932885]

I'm going back to school after dropping out of Uni and to work as a pipe welder in West Texas about 8 years ago

I took Chem 121 but 122 is a requirement for the engineering degree im taking, I don't want to retake the class, what are the highlights I need to study up on to be comfortable taking 122?

Also I took Thermodynamics but forgotten almost all of it. What do I need to know to be OK in Heat Mass transfer?

[Anonymous No.10932976]

In contrast with common knowledge about why birds are not shocked by standing on power lines, I assume that humans can be killed by grabbing a single high voltage AC line (and not connected to any other line or ground) due to their capacitance and being continuously charged and discharged meaning a current is running through them. Am I correct in this assumption? If I am, what voltage lines would be required to kill a human (assuming 50 mA is deadly)? Also, could whoever answers he question show the calculations? I tried doing it but have no idea what even a reasonable amount of time for the time it would take a power line to charge a human would be and if this would be limited by the ac frequency.

[Anonymous No.10933149]

Will it ever happen that large bodies orbiting the sun cross paths or collide? Like Pluto bumping into Mars or something cooler.

[Anonymous No.10933253]

>>10933149
>pluto
>planet
anon...

[Anonymous No.10933334]

>>10933253
I never said planet, fucker. You have destroyed my question.

[Anonymous No.10933340]

>>10917700
No, but if you look closely it resembles the patterns found in inverse hyperbolic functions
https://upload.wikimedia.org/wikipedia/commons/f/f4/Mplwp_inverse_hyperbolic_functions.svg

[Anonymous No.10933341]

>>10933334
Also, pluto IS a planet!

[Anonymous No.10933459]

Economics is math, right?
>Through the '40s, '50s, '60s, gold was valued at $35/t.oz
>$35 in 2019, adjusting for inflation, is $233/t.oz

>the current trading price for gold is over $1500/t.oz
How does that work out?

[Anonymous No.10933485]

>>10933459
demand increased faster than supply

[Anonymous No.10933497]

Will it ever happen that large bodies orbiting the sun cross paths or collide? Like a dwarf planet bumping into Mars or something cooler. Like Halley's comet hitting Jupiter?

[Anonymous No.10933513]

>>10933459
>How does that work out?
literally jews
>>10933497
>halley's comet
>dwarf planet
come on man...

[Anonymous No.10933683]

How can I find the power from this given signal?

I know that power is the integral of that signal squared, so eventually I end up with
e^(2jwt)cos^2(wt)
Using Euler, I end up with (cos(2wt)+jsin(2wt))cos^2(wt))
How would I go about integrating this between T/2 and -T/2?

[Anonymous No.10933807]

I bought some instant noodles with BHT and BHA.
Should I just throw them to the trash?

[Anonymous No.10933831]

Can I become a psychopath at age 20?
I'm getting tired of being a fragile nervous faggot

[Anonymous No.10933835]

>>10933831
You don’t want that.

[Anonymous No.10933853]

>>10933835
could you expand on that?

[Anonymous No.10933863]

>>10933853
You don’t want to be predatory towards friends and family

[Anonymous No.10933915]

>>10933863
possibly not, but I want low cortisol, high testosterone and no stress

[Anonymous No.10933925]

>>10933915
You need to be depressed and anxious for a decade and then stop being depressed, that's it. The depression and anxiety will push you to a point of psychological homeostasis and nothing will bother you.

[Anonymous No.10933938]

>>10933925
is that really true?

[Anonymous No.10934198]

>>10933513
Rrr! Why you do that to me?

[Anonymous No.10934217]

>>10933938
No.

[Anonymous No.10934319]

>>10933683
wouldn't it be easier to write [math]\cos \omega t[/math] as [math]e^{i \omega t}+e^{-i \omega t} \over 2[/math], and do the integration in the complex?

[Anonymous No.10934766]

>>10933683
> I know that power is the integral of that signal squared
It's the integral of the square of the absolute value of the signal. The distinction matters if the signal is complex.

For f(t)=e^jαt*cos(ω0*t) (which is what I think that blurry pic-related says), |f(t)|=|cos(ω0*t)| and |f(t)|^2=cos^2(ω0*t), for which the mean is 1/2 (the integral over a cycle with period T is T/2).

|a*b|=|a|*|b|, |e^jx|=1 for real x, |x|^2=x^2 for real x, cos^2(x)=(1+cos(2x))/2.

[Anonymous No.10935176]

What did Artin mean with this exercise?
Is this supposed to be some joke about how horrible the english language is?

[Anonymous No.10935181]

>>10935176
It's a reference to Derrida's critique of preferring speech over writing. Also, it is an example of how homomorphisms need only respect, not preserve, the given structure.

[Anonymous No.10935182]

>>10935176
It`s just the free group of phonems.

[Anonymous No.10935251]

>>10932885
No one has any clue what Chem 122 is besides you.

[Anonymous No.10935273]

I have a chemistry book that is using the words "subshell" and "orbital" backwards from how they're normally used
example: "this means that there are three different P subshells for a particular orbital"
is this correct or wrong?

[Anonymous No.10935383]

When measuring the vertical position (height) of an object, would you measure it from the top or the bottom? For example, if you are measuring the height of a person in the process of diving into a pool, would the height be calculated based on his head or his feet? Pic related, would the diver's height be 10m or 5m? This is a serious question, I'm not trying to be a baiter like the flies in a jar question, I need to know this so I can make an accurate measurement of height.

[Anonymous No.10935721]

>>10935251
General University chemistry 2

[Anonymous No.10935742]

>>10935181
>Also, it is an example of how homomorphisms need only respect, not preserve, the given structure.
what ?

[Anonymous No.10935783]

Does the human body ever chemically change the water molecules that end up inside of it?

[Anonymous No.10935843]

>>10935742
Ah, my bad. It should say
>not preserve all the details
I wrote the sentence a few times as I kept making stupid typos, and so I broke it. What I mean is that you have the structure of written English and the structure of spoken English, and you map the written version onto the spoken version. It respects the structures, but it fails to distinguish between "be" and "bee", for example.

>>10935783
Ask yourself the this the next time you pee.

[Anonymous No.10935896]

According to my professor, the answer here is 5.
However, I keep getting 20.
I let t=1 because of the delta function, end up integrating 5 between 2 and -2.
Then it's like 20δ(1-t)
Am I missing something?

[Anonymous No.10935904]

>>10935251
gen chem 2: thermochemistry, solubility, introduction to reaction rates and mechanisms, reaction equilibrium fundamentals

[Anonymous No.10935906]

>>10932885
see >>10935904 but maybe go a little further into equilibrium and thermodynamics

[Anonymous No.10935922]

>>10935896
the delta function has the effect of sampling.
[eqn]\int_{(a,b)}f(x)\delta (x-k)dx = f(k)[/eqn]

you're doing an extra integration. The single delta integral just samples.

[Anonymous No.10935935]

Hi guys, does anyone know how to calculate the fourier transform of this sequence? The book suggests that you should use the sum theorem

[Anonymous No.10935942]

OEIS (A047209) says that the series [math]1 - \frac{1}{4} + \frac{1}{6} - \frac{1}{9} + \frac{1}{11} - \frac{1}{14}+\dots[/math] sums to [math]\frac{\pi}{5}\sqrt{1+\frac{2}{\sqrt{5}}}[/math] (equivalently, [math]\frac{\pi}{5}\cot\left(\frac{\pi}{5}\right)[/math]), and i don't understand how either of these answers are derived.

l;ooking at the explicit formula of the sequence [eqn]a_n=\frac{(-1)^{n+1}}{\lfloor{\frac{5n-2}{2}}\rfloor}[/eqn] how do you find the sum for a series that uses a floor function like this?

[Anonymous No.10936000]

Why are there so many npcs

[Anonymous No.10936011]

>>10935942
You don't, usually.
In this case, it's just losing 0.5 at all uneven n, so it's not as horrendous.

[Anonymous No.10936052]

>>10935383
Measure first point in direction of flow. Pic is 5m. If you flip diver in pic and give him a jet pack, it is 10m. Exceptions for clearing the bar. Wtf are we talking about? I was thinking viscosity and flow tubes. But seems applicable to most things.

[Anonymous No.10936140]

>>10935922
So basically, it's just multiplying f(x) by 1 because the area of the dirac delta function is 1?

[Anonymous No.10936141]

>>10935942
It wasn't too hard to see that the sequence is

[math] \dfrac {4} {5} \drac{1} {(-1)^{-n} (2 n+1)-1} [/math]

Also I saw a formula for pi*cot(pi*x) on Wikipedia as a series, but it's one involving n^2.

[Anonymous No.10936146]

[math] \dfrac{4}{5} \dfrac {1} { (-1)^{n} (2 n+1)-1} [/math]

[Anonymous No.10936188]

I have two 3D point sets that form a surface each. Say one set is a reference that is fixed in space, the other i can scale rotate and translate. The shape and extent of the two sets are very different.
I have to scale, rotate, translate one of the set into the reference set such way that it fits the best but do not overlap at any place. By fittingi mean it fills the reference set the best.

I know the iterative closest point method but that is sort of not right for this. Where should i start looking?

[Anonymous No.10936254]

Anyone here familiar with circuits?
I need a refresher.
I need to find I
My initial thought it to combine the two resistors on top.
But after that, I just do (V1-V)/R where R is the combined resistor.
I don't think this is right, there are way too many other variables given. Please help.

[Anonymous No.10936281]

>>10936146
> [math]\frac{4}{5}\frac{1}{(-1)^n(2n+1)-1}[/math]
[math]a_1=-\frac{1}{5}[/math]
[math]a_2=\frac{1}{5}[/math]
[math]a_3=-\frac{1}{10}[/math]

[Anonymous No.10936312]

>>10936281
Faggot

[Anonymous No.10936325]

>>10936254
They give you so much information. The unknowns you have are I and V, that's it.

Whip up two equations using KCL:
(V1-V)/R1 + .1I = V/R3, and V1-(V+.V2)/R2 = I. The first equation has .1I because at the node where I splits into aI, .1I of current must move "left" through V2 into node V.
Solve both simultaneously, only unknowns you have are V and I.

[Anonymous No.10936376]

since waves and particles are just models of the world, how come we try to describe quantum physics in terms of its wave-behavior and particle-behavior instead of just defining a new model that has both of those properties? (or, in other words, instead of saying that there's stuff sometimes behaves like a wave and sometimes like a particle, we instead say that it behaves like a warticle, which can sometimes be modeled like a wave, and other times can be modeled like a particle?)

this seems like an absurdly obvious thing to do, so i imagine it's done, but i can't think of how to word this to google and read up more on it. can anyone point me to some resources?

[Anonymous No.10936530]

>>10936376
Because "waves" and "particles" are merely representations of the same von Neumann algebra of quantum operators, usually obtained from Groenewold-Van Hove or Kostant-Souriau quantization of the classical Poisson algebra. These are colloquially known respectively as the "Schrodinger picture" and the "Heisenberg picture"; "waves" and "particles" are merely labels we put onto these representations for intuition.
At the end of the day, Stone-Von Neumann says that any two irreducible unitary one-parameter representations of the Heisenberg group (i.e. freely generated group on [math]p_i,q_i[/math] with CCR) are unitarily equivalent, and so are any representations you might think up that describes whatever "warticles" are. In other words, it's a futile exercise.

[Anonymous No.10936715]

If I toss λ per square meter on average random objects in an area then start from a random point with no object, what distribution does the minimum distance covered in meters till finding an object random variable have?

[Anonymous No.10937085]

>>10936254
1. V + V2 + I*R2 = V1.
2. I_V2 + I - αI = 0 => I_V2 = (α-1)*I (KCL on the right node)
3. (V1-V)/R1 - V/R3 - I_V2 = 0 (KCL on the left node).
3 equations in 3 unknowns (I, V, I_V2). I=~4.3mA, V=~2.3V, I_V2=~-431μA.

[Anonymous No.10937108]

>>10936715
Poisson.

[Anonymous No.10937159]

Any programming language suited for doing math problems? Writing is too hard , messy and takes too much paper.

[Anonymous No.10937326]

>>10937108
Why? It seems exponential.

[Anonymous No.10937414]

Why isn't my homopolar motor working?

[Anonymous No.10937420]

>>10937159
Depends what type of math problems. Numerical computing? Linear Algebra? Calculus?
Either way Matlab, R, and Python are three examples.

[Anonymous No.10937707]

>>10937420
What about Haskell?

[Anonymous No.10937764]

>>10936530
Great post. I actually understand it (despite not having asked).

[Anonymous No.10937766]

>>10937707
Haskell is an epic meme language.

[Anonymous No.10937831]

Help me with my homework plz.
Σ = {a, b, c}
Let n ≥ 1. How many length n strings over Σ are there that never have the same
symbol occur twice (or more) consecutively?

What is the formula for this sht/is there one?

[Anonymous No.10937935]

>>10937831
You have three possible choices of initial letter, two choices of next letter, two choices for the next one, etc.
So [math]3 \times 2^{n-1}[/math]

[Anonymous No.10937972]

>>10937935
what about : How many length n strings over Σ are there? for n ≥ 0
Having trouble thinking about this. You have 3 choices of letter for each of them.

[Anonymous No.10938059]

>>10937972
[math] 3^n [/math] obviously

[Anonymous No.10938366]

How the FUCK is this wrong? and yes, this IS homework

[Anonymous No.10938371]

>>10938366
Post it rotated correctly and I'll answer.

[Anonymous No.10938379]

>>10938366
>try it again, use the exact the exact same inputs on my calculator
>get different values
>theyre right this time
do calculators shit the bed after a while or something?
>>10938371
I appreciate the concern but Im now a happy camper

[Anonymous No.10938381]

>>10913113

"Intellectually challenged" sounds to me more like "ignorant dumbshit" rather than someone with a mental condition.

[Anonymous No.10938387]

>>10938379
No. While PEMDAS is taught in american schools, calculators operate on the PRANDOM system from Timbuktu, which first does parenthesis, and then does the remainder in whatever order it comes up with.

[Anonymous No.10938398]

>>10938387
even so, I used the same order in the same number of entries, nothing at all changed from the first attempts to the final other than me turning off the calculator for a moment

[Anonymous No.10939185]

>If a circuit has 3 nodes and 2 loops in it, then :
Is this even possible? I've tried drawing it out, but I always end up with 2 loops with 4 nodes.
I'm asked to pick one of the following that's true to the above statement:
a. Nodal analysis will require solving more equations than Mesh analysis
b. Mesh analysis will require solving more equations than Nodal analysis
c. None of these
d. Both Nodal and Mesh analysis will require solving the same number of equations
e. It is impossible to determine which method will require solving more equations
Should it be e?

[Anonymous No.10939191]

can someone tell me what the fuck im doing wrong? how is sigma not 200 psi?

[Anonymous No.10939204]

>>10937414
your circuit isn't really a circuit

[Anonymous No.10939670]

>>10931593
Anyone? I do not need any math background, I would also very much appreciate a rec of a nice survey article.

[Anonymous No.10940010]

Why is the total energy of two protons in the center of mass frame pic related? Only one of the protons move, the other is at rest. But in the center of mass frame they both move with the same speed. So is it not supposed to look like this? E=2sqrt((pc)^2+(m_0 c^2)^2))

[Anonymous No.10940015]

>>10939191
>homework
>amerishit units

[Anonymous No.10940090]

>>10939185

[Anonymous No.10940099]

>>10939204
It's an homopolar motor
https://youtube.com/watch?v=voHz6sxwQ2Q

[Anonymous No.10940219]

Suppose you have an urn with n balls numbered 1 to n and take k out with replacement. What distribution does the random variable representing the higher numbered ball taken out in k tries follow?

[Anonymous No.10940230]

Why is 524.95 wrong?
>524.95 rounded to ones is 525
>525 rounded to tens is 530

[Anonymous No.10940240]

>>10940230
You don't round to ones first. 524.95 is less than half way from 520 to 530.

[Anonymous No.10940242]

>>10940240
>You don't round to ones first
Why?

[Anonymous No.10940243]

>>10940230
rounding 524.95 to the nearest ten is 520. |520-524.95| < |530-524.95|

[Anonymous No.10940246]

>>10940242
Why would you?

[Anonymous No.10940248]

>>10940246
because otherwise I'm ignoring some numbers that have values?

[Anonymous No.10940253]

>>10940248
That's the whole point of rounding.

[Anonymous No.10940256]

>>10940253
>That's the whole point of rounding.
yes but I thought I still had to considered them, staring from right to left...
It's weird but ok

[Anonymous No.10940264]

>>10940010
>Why is the total energy of two protons in the center of mass frame pic related? Only one of the protons move, the other is at rest. But in the center of mass frame they both move with the same speed. So is it not supposed to look like this? E=2sqrt((pc)^2+(m_0 c^2)^2))
For a particle moving at a given velocity you can check that E=sqrt((pc)^2+(m_0 c^2)^2)) and E= gamma m_0 c^2 are equivalent.
Also, because in the center of mass two identical particles have equal and opposite velocities, their contribution to the energy is the same, hence the 2.

[Anonymous No.10940304]

>>10935935
please help

[Anonymous No.10940389]

Why the fuck can't I see any image on /adv/ while everything works nicely on /sci/? This is beyond me

[Anonymous No.10940392]

>>10940389
Werks on my machine

[Anonymous No.10940394]

>>10940392
So it's just me. Weird though that it is specific to /adv/ and not the other boards... Perhaps some extension thinks "adv" stands for "ads" or some stupid shit, gotta look into it...

[Anonymous No.10940395]

>>10940394
solved, uBlock Origin was being a faggot (though the way it singled out /adv/ specifically is still beyond me)

[Anonymous No.10940396]

>>10940394
What doesnt doesnt eork tho is quick reply for some weird reason tho

[Anonymous No.10940446]

>>10940264
How are they equivalent tho? I substituted the definition of gamma in E=m_0 gamma c^2 and I can't get to the other expression of E

[Anonymous No.10940456]

>>10940446
Use that p=m_0 gamma v, solve v^2 in terms of p, write gamma in terms of p and substitute gamma(p) instead of gamma(v) in E=m_0 gamma c^2. Then, you will see that they are equivalent.

[Anonymous No.10940470]

>>10921202
If a dog learns how to rip off someone using a personal loan, sure

[Anonymous No.10940489]

>>10940456
Done, thanks a lot

[Anonymous No.10940573]

If the earth was completely flat, how far should the signal from an average tv station be able to reach and still give a good picture? What are the calculations involved? How far do these signal reach in fact?

[Anonymous No.10941317]

I've gotten stuck on a vector calc problem and started googling stuff.
So apparently, grad*=-div. But laplacian=div grad=- grad*grad, which seems to imply that grad f has norm zero a.e. for harmonic f.

[Anonymous No.10941523]

so I'm a math major and I scored below average on the GRE (49%), yet I have straight A's in most upper level math classes (fuck you probability). I go to a good uni (top 30 in math). Why am I seemingly retarded and smart at the same time? I don't understand how I can be so dumb to get a below average score on a high school math exam.

[Anonymous No.10941636]

>>10941523
You either are an idiot who's been making up for it with hard work and never noticed, have dogshit long term memory, or your uni's grades are inflated (I've heard this is common in top U.S. unis).

[Anonymous No.10941657]

>>10941636
I honestly don't work very hard anon. I do my homeworks on time, and study a few days before the exam and thats about it.
>dogshit long term memory
this may be the case actually
>uni grades inflated
I actually go to a school that was rated as one of the toughest graders (we essentially have no grade inflation)

[Anonymous No.10941695]

how do i write a 500 word doc about how neurontrasmitters impact our fight/flight response through the sympathetic and parasympathetic systems?

[Anonymous No.10941719]

>>10941657
I'm not qualified for talking about dogshit long term memory since mine is somehow good, but you might want to pick up a random linear algebra textbook, open it at the middle, and try to solve the exercises. Repeat with random textbooks until you convince yourself.

[Anonymous No.10941877]

>>10941523
Being "smart" encompasses proficiency at way too many cognitive abilities to say you could be "smart" (just) for being good at upper level maths. As the other anon mentioned, long term memory can also fuck you over and then you are screwed too. And in general many things could act as a bottleneck to have an actually good performance in an exam, your job or other everyday activities. Just a single skill is too little information to tell how intelligent you really are, of course under the assumption that such a thing could be measurable in the first place, instead of just an educated but ultimately very rough guess.
In other words, your (and lots of other people's) cognitive skills can be very, very skewed, and if you want to consider that smart or not is up to you.

Also, just as a little sidenote:
>I go to a good uni (top 30 in math).
>>10941657
>I actually go to a school that was rated as one of the toughest graders
A rating on such a matter when you don't know the scale of their ratings is hard to analyze. Among the highest ranked universities, scores are usually inflated cause risking lowering their students score and thus lowering their average scores could be a blow for the university's aggregate rankings, which a lot of them care maybe a little bit too much about. Stuff like that is why a lot of foreign graduate students from countries without very highly ranked universities and with rather "mediocre" absolute grades (although very high relative grades in their respective unis) in their undergrad studies have a field day when doing their grad studies over at the top ranked universities. I know it's a pretty extreme case since among other (especially highly ranked) American universities the variance in inflation shouldn't be too high, but it's just to show that the absolute score can be rather deceiving to make proper conclusions.

[Anonymous No.10942153]

>>10940256
You do, those numbers you rounded are less than 5 which means the "nearest ten" is down.

[Anonymous No.10942859]

Please help here :
>>10937414

[Anonymous No.10942866]

>>10941695
read about dopamine and norephenephron

[Anonymous No.10942887]

>>10942859
because ur a homo jej

[Anonymous No.10942967]

>>10942859
Try touching the magnet with the copper to complete the circuit

[Anonymous No.10943764]

How do I tell the professor I'm doing my PHD with that I hit a wall that is probably not possible to overcome? I have been working on this for more than six months.

[Anonymous No.10943807]

Why do jews like money so much and hate non jews?

[Anonymous No.10943812]

>>10943764
Don't you meet with him regularly?

[Anonymous No.10943815]

>>10943807
Everyone likes money and everyone favors their in-group.

[Anonymous No.10943844]

>>10943812
I do but I noticed the mistake just lately

[Anonymous No.10944055]

>>10943844
Just tell him then. It's literally his job to help you with this sort of thing.

[Anonymous No.10944081]

>>10943807
They have been practicing identity politics longer than anyone and have grown to be pretty good at it.

[Anonymous No.10944813]

How big of a wooden sailing ship could you get to lift on hydrofoils by wind power alone? I doubt something big like a galleon would but maybe at least a sloop or clipper ship. Could I use the lift equation and substitute the air density for water density to calculate the foil area needed to lift a ship?

[Anonymous No.10945021]

One of my uni classes uses some web service for distributing homework and charges students $90 a person for the ability to get/turn in their assignments. Is this scam normal? Do any of you guys have this? I wouldn't be surprised if he's profiting off of it

[Anonymous No.10945402]

I cant figure out how compositions of trig and inverse trig functions work, am trying my hardest but cant visualize it graphically and just confuse myself. plz no bully, i want to like college math but am brainlet

[Anonymous No.10945407]

>>10945021
Yeah its normal, isn’t it nice being treated like a dumb animal?
>>10945402
Just use a graphing calculator or desmos

[Anonymous No.10945879]

Explain? Why is the result not the same? Left is standard procedure no?

[Anonymous No.10946069]

I'm back begging for help for another week, this time it's pic related.
All tips are appreciated

[Anonymous No.10946098]

>>10946069
I only looked for a moment so I might be wrong, but I guess you can find most of the answers and methods when you look up properties of the convolution operator.

[Anonymous No.10946210]

what do you do when you have so many things/hobbies you want to do, but
>the things themselves either already have a very steep learning curve, necessitating a lot of time and effort invested for marginal gains
or
>the hobby has an exponential learning curve where you are already proficient at the thing/hobby, but to progress further you need to invest a lot of time and effort for marginal gains
so the time required to do just one of your hobbies leaves you with no time for the others, so your proficiency in all of them suffers

[Anonymous No.10946221]

>>10946210
Sounds like you have to lose at some end.
May be you can pick up the other hobby at some point and the gains will come back quickly considering you achieved them at an earlier point.

[Anonymous No.10946223]

>>10946221
>>10946210
And which hobby is likely to remain a hobby long term and which isn't, do you foresee yourself spending time with your hobbies all your life?

[Anonymous No.10946240]

>>10946223
>>10946221
It's rather multifaceted. I've already come to the conclusion that I would need to cut out some hobbies, and so I did. I'm now at the ones that have always been lifelong passions/desires of mine, or will be pertinent to my future career

So I narrowed it down to music, drawing, mathematics, and electronics/electrical engineering stuff/circuits
none of which are known for being very easy. I thought about doing a rotating schedule where I would just do one per day, but then I realized I'm only practicing one every 4 days, which sounds like it would severely handicap progress.

And so I wind up with some stupid paralysis where I can't decide what to do and wind up doing nothing at all

[Anonymous No.10946253]

>>10946240
Why do you value your different hobbies? I think I'd pick one for future career prospects and one to use for relaxation and to 'get away from it all'.

[Anonymous No.10946280]

>>10946253
I've been playing piano since I was 6 (21 now) and have been writing music since I was 12. I don't want to give it up because it genuinely makes me happy and I've been doing it for so long
I'm getting my degree in EE/Signals so anything to do with electronics will help me there. I'm specifically getting that degree because of my history in music, I've always wanted to design synthesizers and signal processing circuits.
As a kid, I hated all math because I told myself I could never do it. I started applying myself in college and it turns out not only do I have a small modicum of aptitude for it, I find its structure and elegance to be beautiful and I have a desire to learn as much as I can about it, and I think I can also apply mathematical concepts to my ideas about signal processing circuits
Then there's drawing. I've always wanted to be able to draw. I suck at it now, but when I look at what I make, I can see promise if I could just stick to it. Unfortunately it's not something you can just hit the books on like math or EE. I've been doing music for so long that I don't actually remember the "I suck at this" phase, I just grew up with it, put in all of my Years of Suck when I was young, learned as I aged, and now here I am. Now as an adult I have to consciously deal with the fact that I suck at visual art and it will be many years until I'll be at what I'd call decent, since I need to consciously plow through my visual art shitty years.

[Anonymous No.10946314]

>>10946280
You can get around the whole issue if you just accept that you'll never be the best drawer in the world. It is perfectely fine to be mediocre in some aspects of life.

[Anonymous No.10947463]

>>10923049
Lusztig is 73 and still going strong!