/sqt/ /qtddtot/ - stupid questions thread

[Anonymous No.11540602]

"Try to stay positive" edition.
Previously >>11522896

>what is /sqt/ for
Questions relating to math and science, plus appropriate advice requests.
>where do I go for other SFW questions and requests?
>>>/wsr/ , >>>/g/sqt , >>>/diy/sqt , >>>/diy/ohm , >>>/adv/ , etc.
>pdfs?
libgen.is (Warn me if the link breaks.)
>book recs?
https://sites.google.com/site/scienceandmathguide/
https://4chan-science.fandom.com/wiki//sci/_Wiki
>how do I post math symbols?
https://i.imgur.com/vPAp2YD.png
>a google search didn't return anything, is there anything else I should try before asking the question here?
https://scholar.google.com/
>where do I look up if the question has already been asked here?
>>/sci/
https://boards.fireden.net/sci/
>how do I optimize an image losslessly?
https://trimage.org/
https://pnggauntlet.com/

Question asking tips and tricks:
>attach an image
>look up the Tex guide beforehand
>if you've made a mistake that doesn't actually affect the question, don't reply to yourself correcting it. Anons looking for people to help usually assume that questions with replies have already been answered, more so if it has two or three replies
>ask anonymously
>check the Latex with the Tex button on the posting box
>if someone replies to your question with a shitpost, ignore it

Resources:
Good charts: https://mega.nz/#F!40U0zAja!cmRxsIoiLFZ_Mvu2QCWaZg
Shitty charts: https://mega.nz/#F!NoEHnIyT!rE8nWyhqGGO7cSOdad6fRQ (Post any that I've missed.)
Verbitsky: https://mega.nz/#F!80cWBKxC!ml8ll_vD2Gbw4I1hSLylCw
Graphing: https://www.desmos.com/
Answer engine:
https://www.wolframalpha.com/
Tables, properties, material selection:
https://www.engineeringtoolbox.com/
http://www.matweb.com/

[Anonymous No.11540604]

~UNANSWERED~

Math
>>11525798
>>11527358
>>11534192 (somewhat confused resolution)

CS+/g/
>>11528591
>>11530555
>>11532018
>>11535880

Physics
>>11524877
>>11535264

Bio+Medicine
>>11525157
>>11527257
>>11540453

Stupid
>>11530359
>>11537362
>>11537402 (dunno where this goes)
>>11538328

[Anonymous No.11541219]

Why is the product of two vectors a scalar?.

[Anonymous No.11541231]

>>11541219
It can be a vector as well.
Look up the cross product.

[Anonymous No.11541234]

>>11541219
There is no such thing as a "product of two vectors".
There are "scalar products" which are, as the name say scalars, "cross products" which work in R^3 and produce vectors and sometimes, especially in machine learning there is a "Hadamard product", which is a vector again.

But in general there is no multiplication on a vectorspace.

[Anonymous No.11541246]

>>11541219
it's just some arbitrary operation which takes two vectors as an output and gives back a scalar. we use, because it's useful for angles and stuff.
we name it "product", because when your vector space is 1-dimensional, it agrees with the usual product of numbers.

[Anonymous No.11541378]

>>11540602
> Derive for the Compton scattering process the recoil electron energy [math]T[/math] as a function of the incident photon energy [math]E[/math] and the electron angle of scattering [math]\phi_e[/math]. Show that [math]\phi_e[/math] is never greater than [math]\pi/2[/math] radians.

Conservation of momentum gives: [math]p_{\lambda'}^2=p_{\lambda}^2+p_e^2-2p_{\lambda}p_e\cos\phi_e[/math]
Conservation of energy gives: [math]E+m_0c^2=E'+(m_0c^2+T)[/math]
Using [math]p_e=c^{-1}\sqrt{T^2+2Tm_0c^2}[/math] and combining those above we get [eqn](E-T)^2=(E')^2=(p_{\lambda'}c)^2=p_{\lambda}^2c^2+p_e^2c^2-2p_{\lambda}p_ec^2\cos\phi_e=E^2+(T^2+2Tm_0c^2)-2E\sqrt{T^2+2Tm_0c^2}\cos\phi_e
[/eqn]
which can be rewritten as [math]T(m_0c^2+E)=E\sqrt{T^2+2Tm_0c^2}\cos\phi_e[/math] or [math]T^2(E^2(1-\cos^2\phi_e)+m_0c^2(m_0c^2+2E))=2TE^2m_0c^2\cos^2\phi_e[/math]. This leads to [eqn]T=\frac{2E^2m_0c^2\cos^2\phi_e}{E^2(1-\cos^2\phi_e)+m_0c^2(m_0c^2+2E)}[/eqn] but it doesn't seem elegant and doesn't explain why the electron scattering angle can't be more than [math]\pi/2[/math]. Not even homework, just a retard trying to self study through a book.

[Anonymous No.11541589]

would someone mine giving a crack at this DE using the method of frobenius? I'm at the point where I'm trying to find the two solutions, and I can't for the life of me find the second one

[math]3xy''+2y'+y=0[/math]

I think one of the solutions is

[math]y=C_1\left(1+\sum _{n=1}^{\infty }\:\frac{\left(-1\right)^n}{n!\left(3n+2\right)}x^n\right)[/math]

[Anonymous No.11541591]

Having trouble with part (c). Tried asking the prof but he said he didn't know either.

[Anonymous No.11541689]

When people say things like "GTA: San Andreas has a physics system that is dependent on its framerate," what do they mean?

How would you design a physics system that is not dependent, on some level, on its framerate?

Or how do you design a physics system that is dependent on framerate, for that matter?

[Anonymous No.11542020]

>>11541689
>what do they mean?
the game's next state is calculated using the time since the last update. if it didn't, your characters moving speed would depend on how fast your pc is. for example, an equation for calculating your new position could look like
newPosition = oldPosition + acceleration * timeSinceLastUpdate
>How would you design a physics system that is not dependent, on some level, on its framerate?
you can use a non-relative clock

[Anonymous No.11542029]

Hi, noob here.

If I'm combining two functions in some way, I understand that the domain of the resulting function is the intersection of the domains of the original functions. My question is what notation do I use to express this? So far I've just been using my words :)

[Anonymous No.11542037]

>>11542029
The mathematical symbol for "intersection" is [math]\cap[/math]. Is that what you mean?

[Anonymous No.11542048]

>>11541689
Let's say you want your game to run at 60fps.
Framerate dependent:
-Only calculate physics, mechanics (health calculation, damage calculation, etc.) and graphics every 1/60 second.
Framerate independent:
-Always calculate physics as long as the hardware allow it (even so, usually they would have a minimum duration, like 10ms or something otherwise it's just wasteful).
-Whenever a new display is requested, the physics and every other mechanics at that time are used.
The main difference is that, in a framerate independent setting, your character can die in-between 2 frames. Meanwhile, in a framerate dependent setting, your character can only die in 1 of the 60 frames.

[Anonymous No.11542069]

>>11541689
I think they're referring to this:
https://www.youtube.com/watch?v=fnqpVEgY4EE (just the first few minutes of the video)
In words "if your framerate drops by half, the speed of everything also drops by half, and if it doubles, the speed of everything doubles."
I recall EoSD also doing this.

[Anonymous No.11542111]

>>11542037
what about the sets of the domains of the two functions though? Like, what's the full definition of that particular intersection/ how would I notate that?

[Anonymous No.11542151]

Let [math]F \subset \mathbb R^n[/math] be a closed set and [math]f: C \to \mathbb R[/math] be a bounded function which is continuous save for a set of measure zero. Show the graph of [math]f[/math] has zero measure in [math]\mathbb R^{n+1}[/math].

I can easily prove this if [math]C[/math] is an [math]n[/math]-dimensional rectangle, but I'm having a hard time to grasp how to generalize for an arbitrary closed set. Hints anyone?

[Anonymous No.11542233]

Let [math]F \subset \mathbb R^n[/math] be a closed set and [math]f: F \to \mathbb R[/math] be a bounded function which is continuous save for a set of measure zero. Show the graph of [math]f[/math] has zero measure in [math]\mathbb R^{n+1}[/math].

I can easily prove this if [math]F[/math] is an [math]n[/math]-dimensional rectangle, but I'm having a hard time trying to generalize for an arbitrary closed set. Hints anyone?

[Anonymous No.11542247]

>>11542111
Not him but why is it difficult? Just let the functions be:
[math]f(x): X_1 \rightarrow Y_1[/math]
[math]g(x): X_2 \rightarrow Y_2[/math]
The combined domain should be
[math]X_3 = X_1 \cap X_2[/math]
Or you can use [math]\dom{f}[/math] to depict the domain of [math]f[/math].

[Anonymous No.11542332]

please for the love of god someone explain what the fuck is going on here

[Anonymous No.11542341]

If you combined a microwave beam (same frequency as a consumer microwave oven) with a coaxial thermal camera, could you use this to quickly scan for moisture content in asteroid mining?

[Anonymous No.11542342]

I'm missing something embarrassingly basic, /sci/.

Here's the definition I was taught in calc 2 (all integrals are Riemann):
Fix a point [math]a[/math] and suppose [math]f[/math] is integrable over any interval of the form [math][a,b][/math]. If [math]\int_a^\infty {|f(x)|d(x)}[/math] converges we say that [math]f[/math] is absolutely-improperly-integrable on [math][a,\infty)[/math], in which case [math]\int_a^\infty {f(x)dx}[/math] is also well-defined (much like absolute convergence of a series implies its regular convergence).

I infer that in such a case, [math]f[/math] must be ('regularly') integrable over any bounded interval [math][a,b][/math]; this is a part of the definition. HOWEVER, there exist functions that are absolutely integrable on a bounded interval but aren't integrable on it; take for example the function which assigns [math]+1[/math] for rationals and [math]-1[/math] for irrationals in [math][0,1][/math].

How come the principle of 'absolute convergence implies convergence' doesn't apply for bounded intervals? Am I mixing up things?

[Anonymous No.11542361]

>>11542332
What's (8)?

[Anonymous No.11542383]

>>11542361
I don't get what's going on with (7) either
I don't really see how changing the upper limit of integration stops this function from being 1 at a and 0 everywhere else

[Anonymous No.11542396]

>>11542383
changing the upper bound makes it so that the argument in (x-a) reaches zero. x-a is only zero for x = a. If the upper bound t is smaller than a, (x-a) wont be zero. If the argument of (this only symbollically written) delta distribution is zero, it yields 1. If the argument wont get zero, it will result in 0.

[Anonymous No.11542403]

>>11542383
also the step functions derivative only exists in the sense of the weak derivative. Its not the actual derivative. Just felt like adding that.

[Anonymous No.11542440]

>>11542111
We have, for example, [math]f: X_1 \rightarrow \mathbb{R}[/math] and [math]g: X_2 \rightarrow \mathbb{R}[/math]. We can then define, for example, [math]f+g : X_1 \cap X_2 \rightarrow \mathbb{R}[/math] by [math]f+g(x)=f(x)+g(x)[/math].
>>11542233
I can't come up with any trick for deriving the general case from that particular. But, if I had to prove that, I would try something like this:
For appropriate [math]A \subseteq F[/math], we can define a measure [math]\mu (A) = \lambda (graph~ f_A)[/math], where [math]\lambda[/math] is Lebesgue measure. [math]B \subset F[/math] with measure zero implies that [math]graph~ f_B \subset B \times [a, b][/math] for some [math][a, b][/math] (since the function is bounded), which also has measure zero, and thus the measure should be absolutely continuous in relation to Lebesgue on [math]\mathbb{R}^n[/math]. Radon-Nykodim guarantees a derivative, which zeroes wherever the function is continuous. Since it zeroes a.e., the entire integral zeroes.
My measure theory is rusty, tho.
>>11542342
Reminder that [math]\int _a ^{ \infty} f(x) ~dx =\lim_{b \rightarrow \infty} \int _a ^b f(x) ~ dx[/math] (this is the definition, btw).

[Anonymous No.11542445]

>>11542396
>>11542403
Thanks it makes more sense now but I still don't see what's going with (9)
like where on earth did the "n - nu(t - 1/n)" come from?

[Anonymous No.11542452]

>>11542440
Forgot to mention, but the sigma-finiteness should follow from the function being bounded.

[Anonymous No.11542463]

>>11542445
I think this somehow converges pointwise to the delta dist, altough im not too sure. I havent ever seen this representation for it. But I mean apparantly yn(t) -> x(t) for n to inf.. I think this is just a really autistic way of defining the delta distribution without any distribution theory.

[Anonymous No.11542475]

>>11542445
If you like, just pretend the thing in brackets is the definition of [math] \mathcal{F}_n(t) [/math]. Think about what its graph would look like: you have zero everywhere, except for a rectangle n units high and 1/n wide. [math] \delta [/math] is then the limit where n goes to infinity, as it says. Now just play around with the step function, and you can re-write the brackets [math]
n-nu(t-1/n) [/math]. Try proving or manually drawing it out yourself to see the equivalence.

[Anonymous No.11542479]

Is it worth changing my track to pre-law so that I may go into IT law? I'm done with how slow and pointless my university's mathematics and computer science track is. I'd rather cut my own balls off than write another paper on the arithmetic logic unit or the importance of black women in programming

[Anonymous No.11542483]

Does anyone have any experience editing PDFs to improve quality? I'm trying to get this PDF to look decent at a reasonable file size before uploading to libgen.

It's a bunch of photocopy scans of a real book (it's an old math textbook). Currently I've used adobe acrobat dc to turn it into black and white (60 MB at this point), then I used imagemagick to up the contrast and compress the images (each page) (balloons to like 500 MB w/o compression, 150 MB with) at 300 DPI. Unfortunately, at this point a lot of quality is lost, if I export each page to a JPG using adobe acrobat, then convert, the quality is a lot better but this will use a lot of disk space and probably more memory. Once I get the scans to look decent I'm just going to replace the cover with the color-scan, OCR it with adobe acrobat, re-number the pages, and add bookmarks.

Also, I should mention I found some ghostscript commands that might reduce the filesize without affecting the quality too much, but maybe there's a better way to do this. I've also read that DJVU is better for a document like this (each page is just a highres scan), any recommended utilities for PDF to DJVU conversion? I've already found http://jwilk.net/software/pdf2djvu but I'm just wondering if there are any others.

Any suggestions?

[Anonymous No.11542485]

>>11542475
>>11542463
Yeah I drew it out then I also realized that I was taking the laplace transform incorrectly (I forgot how to do it for piecewise functions) but I ended up with the correct result after realizing.
Thanks fellas. I feel real stupid now lol

[Anonymous No.11542488]

>>11540602
With the Africa population blowing up, will mankind go backwards if they take over demographically or will there be a mongoloid v. negroid race war?

[Anonymous No.11542493]

>>11542488
>2488
Close but no cigar

[Anonymous No.11542497]

>>11542485
yw~
>>11542488
>2488
Close but no cigar.

[Anonymous No.11542500]

>>11542485
Np. Just remember, the dirac dist is regular. There doesnt exist a L^1 _loc function that generates it. All the representations like F_n only converge in a pointwise sense. Writing the delta dist under an integral is merely symbolic and in a rigoros sense not valid, I think. Ofc youll run into trouble when your lecture introduces it as le funnet function that is inf at one singular point. Those functions dont exist, and its a very pathological object to define and work with. Hence the invention of distribution theory. So heads up, the lecture notes or whatever are brainlet material, not you, anon.

[Anonymous No.11542512]

>>11542500
ISNT regular, my bad.**

[Anonymous No.11542549]

>>11542029
Image you have a game in which a rocket flies at a speed of 1 unit per second. That unit can be anything in your game, like a tile on a map.

Several players might be playing this game. One has a machine that can draw your game at 60 fps, another one plays on his mom's laptop and gets 30 fps. You still want the rocket to move 1 unit per second, though.

The number of frames per second are just the number of snapshots you get. If you filmed a tennis match with two cameras, one at a frame rate X and another at Y, the speed of the ball doesn't change, you just get more snapshots every second.

Game physics should be independent, usually, of frame rate. Many older games were not, which is why they would become unplayable once the CPU was too fast. The unit of time at which physics are calculated are often referred to as a "tick" (like a clock tick) in a game engine. How many frames you get per second should not change how fast the objects move. Often people say that a game "runs faster" with better hardware, but that's nonsense if you take it precisely. It doesn't run faster, it runs more smoothly, i.e. you get more snapshots in the same amount of time, but Minecraft doesn't become unplayable if you have 1000 fps.

[Anonymous No.11542602]

How do you gain confidence?
I'm doing research problems so there is no solutions. And every day my self doubt is really killing me inside.

[Anonymous No.11542619]

How can changes of variables/Diffeomorphisms look when I require |det(Dϕ)|=1? Linear transformations in O(n) obviously work... but what about more complex stuff?

[Anonymous No.11542639]

>>11542602
develop a large ego
worked for me

[Anonymous No.11542648]

>>11542440
Cheers, thank you anon

[Anonymous No.11542657]

>>11540602
Im in second year getting an engineering degree, and started pretty bad,like 7/10 grades ,what are the chances for me to reach a phd and pursue something? I know i only have to work hard but i dont know if my current progress is fixable.

[Anonymous No.11542661]

>>11542233
>>11542440
Other solution that might actually be more simple:
According to a random dude on mathoverflow, you can get it out from Fubini (assuming the function is literally just measurable).
He didn't elaborate, but I've reconstructed his proof as follows:
[math]\chi[/math] is the indicator function for the graph. Then [math]\int _{ \mathbb{R}^{n+1} } \chi d \lambda = \int _{ \mathbb{R}^n} \int _{ \mathbb{R}} \chi d \lambda _{ \mathbb{R}} d \lambda _{\mathbb{R}^n} = \int _{\mathbb{R}^n} 0 d \lambda _{\mathbb{R}^n} = 0[/math].
Seems kinda flimsy, so I'm not sure it quite works.

[Anonymous No.11542663]

>>11542602
Solve something.
At the very beginning of research you _should_ have self doubt. You don't know if you're any good at this yet. You might not be; not everyone is.
The more things you've successfully done, the more you will feel sure that you're capable of doing another thing.

[Anonymous No.11542664]

>>11540602
>>11540604
Is farting just shitting in gaseous form?

[Anonymous No.11542684]

>>11542663
Thanks anon. I guess divide my work into manageable chunks might help. Some are doable and some aren't.

[Anonymous No.11542697]

>>11540602
me feel so dumb, how me get smart

[Anonymous No.11542707]

>>11542697
adderall

[Anonymous No.11542744]

>>11542707
me don't like drugs, they say they have bad effects
me have no money too, no job

[Anonymous No.11542831]

What are /sci/ general tips for writing a paper? Is it even possible not to feel anxious/overwhelmed while doing it?

[Anonymous No.11542838]

>>11542831
What kind of paper are you doing?
Generally I would just start right away (otherwise I would procrastinate). You can always edit the draft to fit a sensible outline later.

[Anonymous No.11542854]

Is this a typo, a serious error, or am I dead wrong?

The [math]\alpha_i[/math] and [math]\tau_j(\alpha_i)[/math] are all elements of [math]K[/math], and [math]K[/math] is a 1 dimensional vector space over itself, so any two elements of [math]K[/math] will be linearly dependent.

[Anonymous No.11542862]

>>11542831
I doubt what you're feeling when you write is actually anxiety, unless you write all your papers at 2am the night before they're due for submission.
The uncomfortable nervous feeling you get when you sit down to write is not usually some kind of worry about something bad happening, it occurs because you try to write but don't actually know what to write.
The solution to this is to prepare before you start writing; do almost all your research up-front, and build the most detailed outline you can tolerate of how you intend to lay out your paper. Then when you sit down to write there's little stress or chance of feeling "overwhelmed" because you know exactly what to do next.

>>11542854
You're misreading it. The COLUMNS of A are linearly dependent over K. A is a matrix. The columns are vectors in K^n.

[Anonymous No.11542877]

>>11542838
It's an undergraduate dissertation on the CS field, i've done the introduction and objectives but my orienter told me to reduce the scope. This means I have to scrap at least half of what I've written or at least contextualize with more specific references. I've separated many new articles by reading their abstracts and now I need to actually read them and see which ones are relevant to my paper. It's been hard not to procrastinate tho, as writing this is a new experience to me, and it's probably the hardest thing I have to do in my week schedule.

[Anonymous No.11542903]

>>11542862
>You're misreading it. The COLUMNS of A are linearly dependent over K. A is a matrix. The columns are vectors in K^n.
goddamn, you stop doing math for a year and literally have to restart from 0

[Anonymous No.11543033]

>>11540602
/his/ chad here with a question about tin foil hats. So I don't know much about physics but the gist of tin foil hats is that they allegedly protect your skull from wave smog. I know from when I make roasted chicken in tin foil it will make the chicken roast at higher temperatures. Now correct me if I am wrong but wouldn't the inside of the tinfoil hat get slightly hotter (I am thinking like 0.1 degree celsius, some infinitismal number like you scientists like to say) when waves enter one side to satisfy the conservation principle? If something goes in, something must go out and it goes out (the side where one's head is) in the form of heat? Explain how correct/wrong I am and the mechanism behind it.

[Anonymous No.11543073]

>>11541378
In QED, scattering amplitudes are computed via the path-integral [math]W[\phi,\Sigma] = \int_{\Phi|_\Sigma =\phi} D\Phi e^{-S[\Phi]}[/math], which receives radiative corrections through Feynman diagrams. Tree-levels amplitudes typically involves a 4-integration over [math]\tilde{G}_0[/math], the Fourier transform of the free propagator/inverse Laplacian. [math]G_0[/math] is in general only a distribution, hence we encounter branch cuts in the complex [math]p_0[/math] plane, such as in the segment between [math]\pm m[/math] for time-ordered [math]G_0[/math]. We can send this segment into [math](0,i\infty)[/math] by a conformal transform, and picking up the residue at the branch point gives rise to a multi-valued amplitude [math]\mathcal{M}({\bf k}-{\bf k}')=\mathcal{M}(|{\bf k}|\cos\phi)[/math] across [math]\phi = \pi/2[/math]. This does not mean [math]\mathcal{M}(\phi)[/math] is undefined for all [math]\phi > \pi/2[/math], but only that it comes from another branch of [math]\mathcal{M}[/math] that the physical scattering process does not detect.
>>11542233
Note that the Tietze extension [math]\tilde{f}[/math] of [math]f[/math] is bounded at infinity since [math]f[/math] is bounded, hence we may extend [math]\tilde{F}:\mathbb{R}^n\cup \{\infty\} \rightarrow \mathbb{R}[/math] to a function on the one-point compactification [math]\mathbb{R}^n\cup \{\infty\} \simeq S^n[/math]. [math]\tilde{F}\in \Gamma(S^n,\mathbb{R} \times S^n)[/math] defines a global section [math]F[/math] on the tautological line bundle [math]S^n\times \mathbb{R}\rightarrow S^n[/math], whose image [math]F(S^n)[/math] is precisely the graph [math]\Gamma_{\tilde{F}}[/math]. Now since [math]F[/math] is a global section and [math]S^n \hookrightarrow \mathbb{R}^{n+1}[/math] is a codim-1 embedding, this induces a codim-1 embedding of the image [math]F(S^n) \hookrightarrow \mathbb{R}^{n+1}[/math]. Now just poke a hole at [math]\infty[/math] and restrict to [math]F[/math].

[Anonymous No.11543141]

What are some good /sci/ related suicide methods?

[Anonymous No.11543157]

>>11543033
>skull from wave smog
schizo babble
>I know from when I make roasted chicken in tin foil it will make the chicken roast at higher temperatures.
acts like a mirror. chicken conducts heat inward, then radiates heat outward. foil reflects radiated heat back inward
> tin foil hats is that they allegedly protect your skull
theoretically, acts like a mirror/scatterer, reflects uwaves outward.
>wouldn't the inside of the tinfoil hat get slightly hotter (I am thinking like 0.1 degree celsius, some infinitismal number like you scientists like to say)
trivially, yes. like a thermal blanket for your body heat
>when waves enter one side to satisfy the conservation principle? If something goes in, something must go out and it goes out
no, it's a mirror
learn the difference between conducted heat and radiated (i.e IR) heat

[Anonymous No.11543230]

How do I represent an expression like this as a binary expression tree?

[Anonymous No.11543234]

>>11543141
Just wait a few decades lol

[Anonymous No.11543238]

Hi /sqt/ I know this is a stupid question, but is it possible to create a cure for the coronavirus using "directed evolution"? You take an animal cell or something, evolve the animal cell to see if it develops resistance to the virus, then attempt to see how the animal cell became resistant to see if it could be a useful cure? Of course the virus might evolve to become resistant to the cure, but it might provide short term results

[Anonymous No.11543246]

>>11543230
The numbers/variables are always the leaf nodes.
If you see 2 + 3, then create a parent node (+) for 2 and 3.
If you see ( + ) * 7, then create a parent node for the ( + ) and 7.
And so on.

[Anonymous No.11543331]

Suppose f(x) is a convex function and x is a real variable. If we now replace x by a complex variable z, would f(z) be a convex function?

[Anonymous No.11543383]

How are you supposed to draw [math]\zeta[/math] by hand? I've tried doing them every way I can imagine and they always just look like a braindamaged L.

[Anonymous No.11543405]

>The true OP are the stupid questions we made along the way

[Anonymous No.11543425]

>>11543383
It's really not that hard.
>inb4 something something paint
This looks worse than when I do it with an actual pen, taking a picture and posting it just fucking sucks.

[Anonymous No.11543513]

Brainlet here, how do I discretize [math]\frac{d}{dx}(a\frac{db}{dx})[/math] in central Euler method?

[Anonymous No.11543665]

For an orthogonal matrix [math]O[/math] (size [math]n \times n[/math]), we all know (by definition) that [eqn]\sum_{k=1}^n (O^T)_{ik} O_{kj} = \delta_{ij}.[/eqn] Is there anything known about this when the sum doesn't range over all [math]n[/math] indices? i.e. [eqn]\sum_{k \in I} (O^T)_{ik} O_{kj}[/eqn] where [math]I \subsetneq \{ 1,\ldots,n \}[/math]. I suppose this could also be equivalently stated as, given two orthonormal vectors, what happens to their inner product if we throw away a few components?

[El Arcón No.11543725]

>>11543425

[Anonymous No.11543734]

>>11543331
you need to define the function on the complex variable, it's not defined there
>extend analytically
well then it won't be real valued unless it's constant, will it? is there even a sense of convexity for such functions? i suppose there probably is.

[Anonymous No.11543739]

>>11543725
>that's how he draws a xi
a xi is a flattened loop, then an epsilon, then a small tail.

[Anonymous No.11543943]

How do you use Taylor polynomials in practice? Do you memorize it for some practical functions or do you sometimes find it on the spot?

[Anonymous No.11544016]

do magnets and radios work in a 'perfect vacuum'? Afaik sound works because the air pressure pulsates at whatever frequency, and then the EM spectrum is basically the same thing but with electrons moving instead of the entire gas of the atmosphere right?

[Anonymous No.11544053]

>>11544016
>EM spectrum is basically the same thing but with electrons moving instead of the entire gas of the atmosphere right?
It isn't. Just like there is a gravitational field that surrounds earth, there is an electric and magnetic field everywhere in space. This is a vector field. At any point, there is an electric/magnetic field vector with direction and magnitude. The behavior of this is governed by Maxwell's equations.

[Anonymous No.11544085]

>>11544016
>do magnets and radios work in a 'perfect vacuum'?
This question is equivalent to "can you see the sun".

>EM spectrum is basically the same thing but with electrons moving instead of the entire gas of the atmosphere right?
No. That idea of an "ether" was commonly held over 100 years ago, but has been disproven. EM waves can move WITHOUT a medium.

[Anonymous No.11544088]

>>11543943
>How do you use Taylor polynomials in practice?
You want to approximate an arbitrary function and you do that by plugging in the Taylor polynomial.
That is how you can, for example, derive steepest descent or Newton's method.

[Anonymous No.11544094]

>>11543331
This question is not meaningful unless you precisely specify how you extend f to the complex numbers.

Take f(z) = 1 If z has imaginary part zero and 0 otherwise.
That function is convex on the real numbers, but not convex on the complex numbers.

[Anonymous No.11544101]

>>11543665
I do not think so.
For example given two arbitrary vectors x and y.
Whatever the crossproduct of the first n-1 components may be, I can choose the last components of x and y such that they are orthogonal.

[Anonymous No.11544110]

>>11542619
That is a really complex question, which basically revolves around this PDE.
https://en.m.wikipedia.org/wiki/Monge%E2%80%93Amp%C3%A8re_equation

[Anonymous No.11544376]

Do you consider psychology a somewhat incomplete or pseudoscience? I am particularly interested in learning about depression. What are the best sources for this?

[Anonymous No.11544397]

>>11544376
I would say it's soft science. Some of its methods are based on statistics, biology and neuroscience. These are okay unless the methods being used are wrong.
Some are just random bullshit that is no better than astrology.
What it needs is a better foundation to be honest.
>I am particularly interested in learning about depression
Just check the articles in high profile journals.

[Anonymous No.11544436]

what does the laplace transform actually do? Something something laplace transform except it includes exponentials as well as sinusoidal components but what, geometrically/intuitively, does that help accomplish?

It transforms problems of integration and differentiation into problems of multiplication and division. Why? How? What is it about multiplying a function with exp(-st) and integrating with respect to t that forces problems of calculus to turn into problems of algebra?

[Anonymous No.11544443]

what does the laplace transform actually do? Something something fourier transform except it includes exponentials as well as sinusoidal components but what, geometrically/intuitively, does that help accomplish?

It transforms problems of integration and differentiation into problems of multiplication and division. Why? How? What is it about multiplying a function with exp(-st) and integrating with respect to t that forces problems of calculus to turn into problems of algebra?

[Anonymous No.11544444]

I have triple checked this and I don't know why I don't find the right angle.

>sinA = 6*sin33/4

I find A = 83
But the solving book says A = 54.8 to 1 d.p.

What am I doing wrong?
Thanx sci-anons.

[Anonymous No.11544446]

>>11544444
radians or degrees

[Anonymous No.11544448]

>>11544446
>"find angles in degrees to 1 d.p."

Degrees. My calculator is in degrees too.

[Anonymous No.11544459]

>>11544448
>My calculator is in degrees too
Celcius or Fahrenheit?

[Anonymous No.11544464]

What is the "hello world" of machine learning?

[Anonymous No.11544465]

>>11544444
Very nice digits

[Anonymous No.11544471]

>>11544465
I just want to move on with my trigonometry.

[Anonymous No.11544503]

>>11544464
letter recognition

[Anonymous No.11544507]

>>11544471
Nerd

[Anonymous No.11544516]

Is there any intuitive reasoning why the difference of the antiderivative values at two points equal to the area of the function?
I get all the proof down on why it works, but it still feels weird.

[Anonymous No.11544534]

>>11544516
I find the visual guides to explain it pretty well. The result of a an antiderivation is a curve where y denotes accumulated value (adjust for multivariable)

[Anonymous No.11544543]

>>11544464
>What is the "hello world" of machine learning?
Learning an XOR.

>>11544503
Far too complicated.

[Anonymous No.11544547]

>>11544376
>Do you consider psychology a somewhat incomplete or pseudoscience?
That depends. If you are doing data driven analysis of phenomena it can be a legitimate science.
If you are just philosophizing about how you think stuff should work it isn't.

The issue about psychology is that it is relatively easy to bullshit about it, since it investigates an enormously complex and very badly understood subject.

[Anonymous No.11544562]

>>11544516
f(x) is some function F(x) is the area under the graph measured from some fixed end point (you know what I mean). the derivative is by definition
[eqn]F'(x) = \lim \frac{F(x+h)-F(x)}{h}[/eqn]
when h is small, the area F(x+h) - F(x) is approximately a rectangle. therefore this area is the product of the sides of this rectangle. one side is h, the other side is f(x). the fraction in the derivative definition is clearly the formula for the other side. therefore F'(x) = f(x).

I've made some stupid picture.

[Anonymous No.11544586]

>>11544444
Ah shit, it was the arsin all along.

>sin(b) = a
>b = arcsin(a)

Fuck me, I spend an hour looking for this.

[Anonymous No.11544629]

>>11540602
Germanium has been added concentrations of donor and acceptor
>Nd=1.55*10^16 cm^-3
>Na=1.5*10^16 cm^-3
Determine the concentrations of cavities and electrons at a temperature of
>67C -> 340.15K
where the forbidden belt width of Germanium is
>Eg=0.64eV
the semiconductor constant is
>C=1.61*10^15 K ^3/2 cm^ -3

now.... I know that formula Et or energy temperature equivalent goes like this
>Et=T/11600 eV
= 340.15/11600 =0.02932327586eV

now for intrinsic concentration
>ni=C*T^[3/2]*e^[-Eg/2Et]
and I get
ni=1.61*10^15K^[-3/2]cm^(-3)*340.15^[3/2]*e^(-10.91405)
now I am not sure what I need to get there as the correct result
I know that the semiconductor is type N since there is more donors than acceptors

electron concentration
non=[ (Nd-Na) + sqrt[(Nd-Na)^2+4ni^2] ] / 2
cavities
pop=[ (Na-Nd) + sqrt[(Na-Nd)^2+4ni^2] ] / 2

how much is ni?

[Anonymous No.11544670]

>>11544516
>these other answers
It's very simple: the rate at which the area under a curve changes is proportional to the height of the curve itself.

[Anonymous No.11544729]

I had the shittiest Migraine today, puked like 10 times and lasted 5 hours, couldn't sleep but now the pain is gone.
Should I Study or just chill for today to let the "headache hangover" go away, to be honest, I feel like I wouldn't learn shit, but maybe that's just laziness.

[Anonymous No.11544741]

>>11544729
*Yesterday, you know I couldn't sleep because I still believe it's "today"

[Anonymous No.11544761]

well my boss is off due to the wu tang flu infecting her husband and ive got a new tickly cough, which is fun. will having vinegar with my food (i tend to drench my fish in it when i eat fish) help my stomach kill any that wind up going down there? i tend not to sip so much as chug water so i wonder if i wont be increasing my risk of getting it in other places than just the lungs, which i assume makes it worse.

[Anonymous No.11544764]

>>11544761
this is all assuming i do have it and not that ive just inhaled more dust or cleaning product than usual from my job and my lungs want rid of that shit

[Anonymous No.11544797]

>>11544761
Do you have a fever? if not fuck off.
If you have it be grateful that it will be "just the flu bro" for you.

[Anonymous No.11544890]

>>11544729
>>11544741
Instead of being a total piece of shit, you should at least put on a classic movie or start a good novel

[Anonymous No.11544972]

>>11544729
>>11544741
Instead of being a total piece of shit, you should at least put on a classic movie, or start a good book. You may go for a walk.
>>11544443
>what does the laplace transform actually do?
It maps a function of time to a function of [math] s=\sigma+j\omega [/math]; AKA time domain to frequency domain.
>but what, geometrically/intuitively, does that help accomplish?
Say [math] y [/math] is a real function of time. Its graph is a depiction of how magnitude changes with time. [math] \mathcal{L}\{y\} [/math] is a complex function, however, with both a magnitude and phase. Its graph shows how the magnitude and "direction" of a signal changes with frequency. If you are trying to figure out how the voltage over a passive component changes with the frequency of an input voltage somewhere else in a circuit, a log plot of the ratio of the Laplace transforms of output to input gives you a very quick and handy way to visualize the relationship. Much, much easier than working with ODEs in the time domain.
>What is it about multiplying a function with exp(-st) and integrating
The only functions that can be transformed are of exponential order. This means that for [math] y(t) [/math] there exists some large [math] T [/math] and constants [math] k, c [/math] such that [math] |y(t)|<M\exp ct [/math]. It can be shown that polynomials, rational functions, trig functions, exponential functions themselves, etc. are all of exponential order [math] -s [/math].

[Anonymous No.11544997]

>>11544972
|y| < M*exp(ct) for t>T, ofc

[Anonymous No.11545006]

Please someone help:
Find in terms of p and q, the coordinates of the midpoint of the line joining C(p, q) and D(q, p). Hence show that O(0, 0) is on the perpendicular bisector.

Midpoint was straightforward: M[(p + q)/2, (p + q)/2]. I then thought all I needed was to show perpendicularity using the two gradients. Slope of CD = (p - q)/(q - p) or (q - p)/(p - q), but when I find the gradient of OM (which is 1), I see that the product of CD x 1 doesn't equal the negative reciprocal, as it should.

I've tried all sorts of silly algebra which I won't bore you with... but I think something really basic is flying over my head.

[Anonymous No.11545168]

>>11545006
Don't worry lads. Just had a fresh look at this and solved it. Gradient of CD = (p - q)/(q - p) = - (q - p)/(q - p) = -1. Annoyingly, this was the first thing I thought to do, but dismissed it for what turned out to be completely unproductive algebraic manipulations.

[Anonymous No.11545278]

Can we do this even though the limit on the LHS doesn't exist? If so, could someone provide a proof?

[Anonymous No.11545285]

>>11545278
If the limit on the LHS doesn't exist than neither does the other one. I don't think it means anything to do that.

[Anonymous No.11545294]

>>11545278
no. I mean there's nothing "to do". the limit simply doesn't exist.

[Anonymous No.11545313]

>>11545285
>>11545294
Thanks. If we were to say x > 0, would it make the limit on the LHS exist? I'm not sure what happens when there's nothing on one side of the limit.

[Anonymous No.11545330]

Taking cal iii rn
Can you pull a constant all the way out of a double integral?, ie
does Int(int(Ax dx dy = A* int(int(x dx dy

[Anonymous No.11545341]

>>11545313
>If we were to say x > 0, would it make the limit on the LHS exist
Yes, gaurentee.

[Anonymous͘ No.11545361]

Help /sci/ , i'm stuck. , How do i prove this by induction ?

[Anonymous No.11545412]

>>11545361
The weird thing is if i keep it the way it is it doesn't work , but if i assume (n-1) and try to prove n it doesn't work

can someone help ?

[Anonymous No.11545463]

>>11545278
>>11545285
NO, that's not true. here the limit on the left hand side doesn't exist, but the limit on the right hand side does.
there's just not this equality between them,

[Anonymous No.11545473]

>>11545313
no, the limit on the LHS wouldn't exist. the limit on the RHS would exist and it would be infinity.

the theorem which you want to use is:

if both limits of f and g exist, then so does the limit f*g and is equal to lim f * lim g (unless of course this isn't indeterminate)

notice that this is a one way implication. if the limit of f*g exists, it doesn't tell us anything about the individual limits of f and g.

[Anonymous No.11545491]

>>11545361
What have you tried?

[Anonymous No.11545497]

>>11545330
Yes. The integral is a linear operator, so you can pull it in front of the first integral, but then also in front of the second one.

[Anonymous No.11545502]

>>11545497
Thats what i figured, thanks

[Anonymous No.11545520]

>>11545278
For x_0 not 0 this can be done, a question which was basically the same came up in the last thread.

BUT you do not know in general that if one of the limits doesn’t exist, then the other doesn’t too, an example was provided in the last thread.
E.g. replace the square function with the sigmoid, the left side would exist, but not the right side.

[Anonymous No.11545529]

>>11545473
>>11545520
What about pic related? That was my follow-up question, but I might not have expressed it clearly.

[Anonymous No.11545534]

>>11545529
yes, because the formulation implies that x is allowed to approach 0 only from the right. the limit is +inf.

[Anonymous No.11545536]

>>11545473
>would exist and it would be infinity
Please read up on your analysis.

> the theorem which you want to use is:
You can use a different one, see the last thread for example.

[Anonymous No.11545543]

>>11545361
>>11545412
>>11545491
Don't sweat it guys figured out my error

[Anonymous No.11545550]

>>11545534
>>11545529
No. Since the function becomes arbitrarily large the limit doesn’t exist.
And no it doesn’t “equal infinity “ infinity isn’t a number and a limit existing means it is a real number.

[Anonymous No.11545579]

>>11545534
OK, thanks. I guess it was simply implied from context that the value was supposed to be positive in my textbook then.

>>11545550
Assuming x is element of (0,inf), would the equation in >>11545278 hold even though the limits don't exist?

[Anonymous No.11545582]

>>11545550
Continuing >>11545579
I mean, it is used in practice. Pic-related is where my question comes from.

[Anonymous No.11545584]

>>11545536
>>11545550
well, in my native language I'm used to saying "lim exists and is finite" or "lim exists and is infinite".
it's just terminology. you can easily make the word "equal" justified by working with the extended real line.

[retard No.11545615]

Any good sauces on continued fractions, please?

[Anonymous No.11545689]

>>11545584

Indeed, this is just an ambiguity in the language of the question. It's like asking "is zero a natural number?". Well it depends on the author.

[Anonymous No.11545854]

>>11543234
why wait when i could do it now though

[Anonymous No.11545885]

>>11543665
You're asking if [math]O\in O(n)[/math] implies [math]P_kOP_k \in O(k)[/math] where [math]P[/math] is the projector into the k-subspace. The answer is no, for if this were the case then [math]P_1OP_1 \in \mathbb{R}
[/math] must be [math]\pm 1\in O(1)\cong\mathbb{Z}_2[/math], but the embdedding [math]O(k)\hookrightarrow O(k+1)[/math] into the upper-left block implies then that [math]O = \operatorname{diag}(\pm 1)[/math] for every [math]O\in O(n)[/math], an obvious contradiction.
>>11544443
Geometrically Fourier transform sends [math]G[/math] to the space of its (irreducible) characters [math]\widehat{G}[/math]. Functions on [math]G[/math] inherits an induced action [math](g\cdot f)(g)= f(a^{-1}\cdot g)[/math] for [math]a\in\operatorname{Aut}G[/math], the same is particularly true for [math]\chi\in\widehat{G}[/math]. Consider translations [math]a\in A\subset G[/math], then [math](a\cdot \chi)(g) = \chi(a^{-1}\cdot g)= \chi(g-a)[/math]. But as [math]\chi[/math] is a group homomorphism we have [math]\chi(g-a) -= \chi(g)\overline{\chi(a)}[/math] a multiplication. This extends to every function [math]\hat{f}[/math] on [math]\widehat{G}[/math] in the [math]L^1[/math]-span, i.e. functions such that [math]\hat{f}(\chi) = \int_{G}d\mu(g) f(g) \chi(g)[/math] for some function [math]f [/math] on [math]G[/math].
Now translations are generated by differentials, while multiplication is generated by multiplication, hence [math]\partial_a \in \operatorname{Lie}A[/math] is sent to [math]M_{\overline{\chi(a)}}\in \operatorname{Lie}\widehat{A}[/math]. This means that differential operators [math]P[/math] on [math]f[/math] is sent to a multiplication operator [math]\widehat{P}[/math] on [math]\hat{f}[/math]. Fourier-Wiener, which is a generalization of Laplace, is a generalization of this to case where [math]\chi[/math] does not necessarily take values in [math]U(1)[/math].

[Anonymous No.11545930]

Cross posting this since it seems like /eeg/ is dead, or too busy with real problems to entertain my noob shit
>>11545728

[Anonymous No.11546101]

>>11545854
Why do it now when you could wait? (This is not a rhetorical question.)

[Anonymous No.11546118]

>>11546101
because living is painful

[Anonymous No.11546128]

>>11546118
What ails you more specifically, anon?

[Anonymous No.11546135]

>>11546128
loneliness

[Anonymous No.11546207]

>>11544516
You can see the integral as the limit of a summation as in pic-related. Every rectangle would have height f(x) and width dx, with dx->0. Then, the same principles you can use with summation apply. That is, if you have a sum, such as [math] \sum_{n=-\infty}^{\infty} a_n [/math], but only want the values between a and b, you would do [math] \sum_{n=-\infty}^{b} a_n - \sum_{n=-\infty}^{a} a_n [/math]. You should be able to visualize this.

[Anonymous No.11546226]

>>11546135
Loneliness can be managed, anon. You can learn to live and be comfortable with it. You can also reach out to people. If you're in a situation where there's absolutely no one close to you right now, you could join a new community, either by physically changing from one city to another or by talking to people on forums, etc. If you're the new guy, then it's normal to not know anyone and you have a chance to integrate and become more or less a normal member of whatever community you chose.

[Anonymous No.11546255]

>>11546207
To simply further, to get the area between a and b, you compute all the area up to b and substract all the area up to a. That is the difference you're actually making, because that is what the the values you are using represent: all the area up to that point.

[Anonymous No.11546355]

>>11546226
i'm also autistic so thats another heavy load to bear

[Anonymous No.11546402]

OK, this is going to be pretty fucking autistic, but bear with me.
If I look at modules over a commutative ring [math]R[/math], I can take their direct sum and tensor product. Direct sum is commutative and the identity element is just the zero module,. I can't really say I have inverses so it's only a commutative monoid. Meanwhile the tensor product distributes over direct sum and has identity element [math]R[/math] as a module over itself. Not sure if I can say that it's commutative, we do have that [math]A \otimes_R B \cong B \otimes_R A[/math] so maybe it is commutative.
So can I say that this thing is a commutative semiring with identity? Am I even making any sense?

[Anonymous No.11546459]

>>11546355
> In the developed countries, about 1.5% of children are diagnosed with ASD as of 2017.
And one that is shared by many others. I'm sure they're are some autism-friendly organizations or groups you could join to help fighting your loneliness. Try to look into it once again before resolving to suicide. You can always kill yourself another day. You still have some options to further explore.

[Anonymous No.11546538]

>>11546402
I mean you'll need to quotient by the module isomorphism equivalence relation, but after that probably.

[Anonymous No.11546551]

>>11546226
>Reddit: the post
Why is it when anyone mentions personal problmes like that, some faggot gets preachy.

[Anonymous No.11546625]

>>11543665
Suppose [math]P[/math] is a projection operator onto a subspace of a vector space [math]V[/math] with inner product.
Then, naturally, [math]I-P[/math] is the projection onto the subspace orthogonal to [math]P[/math]'s image.
Finally, we obtain the "generalized Pythagoras" formula [math]\langle u, v \rangle = \langle Pu + (I-P)u, Pv+ (I-P)v \rangle = \langle Pu, Pv \rangle + \langle (I-P)u, (I-P)v \rangle[/math]. In particular, consider [math]u = (1, 1)[/math], [math]v = (1, -1)[/math] , and [math]P[/math] as projection onto the first entry.
>>11542341
>quickly
Probably not.

[Anonymous No.11546652]

>>11546538
oh yeah of course need to do that
did some reading, turns out the direct sum part is actually a thing

[Anonymous No.11546678]

>>11545930
Do you not have the beta right there?

[Anonymous No.11546709]

>>11546551
What would you have me do? Hand him a rope? Ignoring someone who just mentioned being suicidal because of loneliness doesn't seem any better.

[Anonymous No.11546881]

graduated in december, starting grad school in the fall for amo physics. should i brush up on general physics and math during the long wait, or maybe just look ahead to courses i will take and research papers in the field?

[Anonymous No.11547030]

>>11543383
I always find greek bullshit easier to draw from the bottom up

[Anonymous No.11547050]

>>11544543
Too basic

It's classifying the Iris dataset.

[Anonymous No.11547087]

>>11545582
If it goes to infinity it is called DIVERGENT and it is said the limit doesn’t exist.
The = inf is a shorthand for it grows infinitely large.

[Anonymous No.11547091]

>>11547050
>Too basic
A hello world program is never too basic.

[Anonymous No.11547141]

>>11546459
i worry that once i graduate i won't be able to find a job. if i go unemployed things will look pretty grim for me. no friends. no girlfriend, no job, there's hardly patching that

[Anonymous No.11547287]

Can someone help me solve this system of logarithmic equations for t_0 please.
a. [math]1=C(ln(t_0+2)-ln(t_0))[/math]
b. [math]2=C(ln(t_0+1)-ln(t_0))[/math]

[Anonymous No.11547300]

>>11547287
Apply exp to both equations and see what happens.

[Anonymous No.11547339]

>>11547300
It gives me a polynomial which has no real roots if I do it like in pic related but if I take the 3rd line as e^(ln(t0+1)+ln(t0)) instead it gives me t_0=1 which I know for a fact it isn't.

[Anonymous No.11547351]

>>11547339
>It gives me a polynomial which has no real roots
Seems plausible. Without doing any kind of investigation I would say that you shouldn’t expect a solution to exist.

[Anonymous No.11547379]

>>11547351
guess I'm going about the question the wrong way then. thanks for your help!

[Anonymous No.11547464]

>>11547379
It does have complex roots though if you're really jonesing for an answer.

[Anonymous No.11547589]

>>11540602
Hey anons. Can someone tell me what the hell is going on in this paper?
https://ieeexplore.ieee.org/document/8456164

[Anonymous No.11547647]

haven't touched this in a few weeks because of extended spring break, but these are our notes for the next chapter. why is the standard deviation s different from the standard deviation given? I can't find any notes that say how to find s from the given standard deviation
I tried [math]\sqrt{30}*\frac{3}{4.09} = 4.0175[/math](found 4.09 by multiplying 2 by t table value of 2.045)
is this just a rounding difference?

[Anonymous No.11547724]

Are there any combinations of common/semi-common household products that react hypergolically?

[Anonymous No.11547809]

help

[Anonymous No.11548045]

>>11547589
ANYONE ??

[Anonymous No.11548091]

>>11547589
The authors can tell you. It is called an "abstract".

[Anonymous No.11548234]

Hi I'm learning math. What's the function that describes the slope of a line based on some angle theta?

[Anonymous No.11548256]

>>11548234
That function should normally be (difference in y) / (difference in x).
Now with theta, the differences should be [math]hypotenuse\times\sin\theta[/math] and [math]hypotenuse\times\cos\theta[/math]

[Anonymous No.11548260]

>>11548256
[math]h \times \sin \theta[/math] and [math]h \times \cos \theta[/math]
h = hypothenuse.
The math didn't show for some reasons.

[Anonymous No.11548274]

>>11548260
thank you

why do we multiply by h?

[Anonymous No.11548282]

>>11547141
What are you studying?

[Anonymous No.11548291]

>>11548274
Well, you don't have to actually because the h will be cancelled out when we do the division. I was being redundant. Sorry.

[Anonymous No.11548301]

>>11548291
no that's fine I wasn't even thinking about that, I was just curious, thanks again

[Anonymous No.11548563]

>>11548091
Yeah I read the abstract. But I mainly don't understand the the 3 algorithms explained in the paper

[Anonymous No.11548863]

What's a good first programming language? I'm thinking of python for working with sage.

[Anonymous No.11548927]

I'm a senior in math taking calc 1 (long story). I can't for the life of me get an A on the exams in this class, always B. Am I fucking retarded? I got a high A in real analysis and A's in most of my other upper level math classes. It is absolutely infuriating that I cannot get an A in fucking calc 1 of all classes. What is wrong with my brain?

[Anonymous No.11548950]

>>11548863
If you already have a specific project or job you want to do, look up what programming language they're using in the industry. For example, if it's to make games, C++ would probably be the best choice.

If you're not sure, it doesn't matter. Ultimately, you can start with wathever language. Python is a good first programming language to learn. You can quickly test out things, no need to compile or even write a complete program. You can just type something in the interpreter and you'll have immediate feedback. This makes it a lot more fun for beginners. It's well documented and you have a lot of librairies for whatever project you'd wanna build.

[Anonymous No.11548954]

>>11548927
Meh. Math exams are shit anyway. You could misread the question and get it wrong. So you get a B for misreading one question. Who cares.

[Anonymous No.11548958]

>>11548950
Ya that makes sense. I think I want to do it for fun and I do have some projects in mind. Mostly modeling with dynamics.
I'm a math major, so I also just think it would be a good idea to have some coding competence in like python or java or javascript or something to have a few more options for jobs after I graduate (since I certainly won't be able to get into grad school with my straight B average).

[Anonymous No.11548981]

>>11548958
Yeah, that's a good idea. I think python is used a lot in academia for scientific computing. Learn the basics of the core language itself, then look up libraries such as numpy, numba, matplotlib, scipy, etc.

[Anonymous No.11548989]

>>11548927
How is everyone else in the class doing? It could be the problem in the prof/exams as well.
Calc 1 is basically plug and chug and tricks, so it shouldn't be harder than real analysis. It needs a different skill set though.

[Anonymous No.11549081]

>>11548958
I almost forgot. I saw a book a few weeks ago that looked interesting. Haven't read it yet, but it could be just what you want.
https://www.amazon.com/Dynamical-Systems-Applications-using-Python/dp/3319781448

[Anonymous No.11549090]

>>11549081
That's beautiful! Thanks a lot.

[Anonymous No.11549098]

what's the difference between interior and relative interior? Isn't [math]aff(X) \supseteq X[/math] ?
I don't see why intersecting the interior with the affine hull would make a difference.
Perhaps in infinite dimension?

[Anonymous No.11549146]

>>11548282
i'm doing engineering

[Anonymous No.11549195]

Can we actually "hear" drum modes with [math] m \neq 1 [/math]? It seems like all modes except those with [math] m = 1 [/math] possess odd symmetry about the origin, so in the limit as you move further away all the longitudinal sound waves from a (finite) vibrating drum head should destructively interfere.

[Anonymous No.11549269]

>>11540602
can someone read the signature? or know who the illustrator is?

[Anonymous No.11549289]

>>11549146
I wouldn't worry too much about finding a job, then. You might not find your dream job, but you wont be in the streets.

[Anonymous No.11549359]

>>11549195
On domains with high symmetry you definitely can, as solutions are characterized by their [math]L^2[/math]-reps and you can count the order of the symmetry of the domain by counting degeneracies of each eigenmode. The short answer in general, however, is no. What we know in 2D is that we can hear the shapes of the drums up to a certain "triangulated equivalence": domains are Laplace-isospectral iff solutions local on each 1-simplex can be patched across them satisfying certain consistency and boundary conditions. See https://arxiv.org/abs/1101.1239..
Now intuitively this tells me that the answer would also be no in arbitrary dimension (indeed it is also no in 3D): just topologically, the triangulated domains are characterized by Pachner moves which grow in dimension, and these must be necessarily weaker than the above triangulated equivalence. Hence the space of triangulated equivalent domains would also grow in dimension. This means that we'd be less and less accurate in determining the shape of the drumhead given its sound.

[Anonymous No.11549502]

How do I do this with two power sources? Do I just do each power calculation separately?

[Anonymous No.11549529]

is 4.5 yo too young to start teaching my little sister calculus?

[Anonymous No.11549536]

>>11549529
Depends. Does she know algebra yet? No such thing as too young, depends on how retarded she is or isn't. Besides, even high school calculus isn't that hard.

[Anonymous No.11549537]

>>11548234
That's just the tangent function.

[Anonymous No.11549542]

>>11549529
teach her abstract algebra instead its easier

[Anonymous No.11549552]

>>11549502
>Do I just do each power calculation separately?
Basically, yeah. Use superposition.

[Anonymous No.11549570]

>>11549269
>glo*e
Writing like a true doctor. I tried looking them up on https://ami.memberclicks.net/member-directory#/ without success, but I only looked at the family names since those are sorted alphabetically.

[Anonymous No.11549574]

>>11549552
So correct me if I'm wrong.
I've got S1 = (V1^2)/R + j(V1^2)/X and S2 = (V2^2)/R + j(V2^2)/X.
S1 = 14400∟-10 + j2057∟-10 and S2 = 10000∟0 + j1428.6∟0.
What do I do now? Do I just subtract S2 from S1 and the remainder is the power dissipated by the line? How do you determine which source is the supplier and which is the receiver?

[Anonymous No.11549603]

How would I perform a DC analysis on a voltage divider biased transistor where R1 is shorted? My textbook's troubleshooting section only describes open fault analysis, nothing on shorts

[Anonymous No.11549611]

>>11549574
Ignore the angles. I forgot you only use the absolute values for V. So S1 = 14400 + j2057 and S2 = 10000 + j1428.6. How do you know whether to add them or subtract them though?

[Anonymous No.11549650]

>>11549574
>>11549574
You know V1. You know V2. You know Z. The current through the line is (V1-V2)/Z. Complex power is V*I, or S=(V1-V2)*I. Now you get that real power is the real part of S and reactive power is the imaginary part.
>>11549603
Just do mesh analysis and apply KVL. Assume IC and IE run clockwise, then [math] I_B=I_E-I_C=I_C/\beta [/math].

[Anonymous No.11549675]

>>11549650
Thanks for the help. Isn't S = VxI* (conjugate of I)? Also that will give me the power loss in the line right? What about the power supplied/received by each source?

[Anonymous No.11549731]

>>11549650
>Just do mesh analysis and apply KVL.
Well that would be completely out of left field since the textbook doesn't do anything like that, are you sure there's not a quicker solution? I've solved every other problem using the formulas from the textbook, mostly pic related besides working in cutoff and saturation.

[Anonymous No.11549732]

>>11549675
Yes, my bad. And you will also need a factor of 1/2 since we did not directly compute RMS voltage/current.

[Anonymous No.11549736]

>>11549732
Thanks. What about the power supplied by the sources though? Would that just be 1/2xV1xI* and 1/2xV2xI*?

[Anonymous No.11549740]

>>11549731
Looks like they did nodal analysis instead of loop. It doesn't matter.

[Anonymous No.11549745]

>>11549736
>Would that just be 1/2xV1xI* and 1/2xV2xI*?
>

[Anonymous No.11549761]

>>11549745
The value I get for the line seems reasonable enough. I get S = 1.743 + j 12.265 but the values for the sources don't seem to add up. S1 - S2 should equal S shouldn't it? I get S1 = 124.21 + j 138.44 and S2 = 93.06 + j 123.95

[Anonymous No.11549774]

What causes galaxies to move around in space? Is the milky way being pulled towards something, and if so, what? Or if it's the remaining effects of the Big Bang, how? Why is the Andromeda galaxy and the milky way set to collide, are they moving towards either other or in similar directions that eventually intersect?

[Anonymous No.11549786]

How hard would it be to cobble together an infared vein finder like pic related?
It doesn't have to work as well as a retail one and I want to do it as a fun project.

[Anonymous No.11549790]

>>11549786
bro just use your eyes lmao

[Anonymous No.11549854]

>>11547091
but what if it was written in BASIC?

[Anonymous No.11549864]

>>11549740
Pretty sure there's something else to this, shouldn't be complicated. Thanks for trying to help anon.

[Anonymous No.11549883]

>>11548927
>long story
Care to share, anon? No judgement, just curious.

[Anonymous No.11549947]

So are cloth masks that are now being recommended simply to reduce the amount of particles spread from coughing/sneezing? i.e., it's to help reduce the spread from people who have COVID-19 and are in public? Because I don't think it would do much good for a healthy person. If someone sneezes on you, I don't think it will matter much if you have a cotton mask on. Am I right in thinking this?

[Anonymous No.11549956]

>>11549947
This is precisely the motivation for wearing them. They do jack shit on their own to prevent you from getting sick, but if you're sick (even if you don't know it) they prevent you from spraying your coof everywhere.

[Anonymous No.11549968]

>>11549956

Okay that's what I thought. So I'm not super worried about going into the store without one, although it might be a jackass move if I somehow have it.

[Anonymous No.11550053]

[math]
\lim_{n \to \infty} \frac{2^n}{3^n}
[/math]
??


show steps

[Anonymous No.11550054]

>>11549740
So looks like the relevant information was actually in an older edition of the textbook, professor just have forgot to teach it. Basically, since the transitor is driven so hard into saturation, you can assume VCE is approximately 0. With that, everything falls in place, IE comes out to 8.3mA and IC computes as 319uA using >>11549731 these formulas. Almost exactly matching multisim.

Thanks for trying to help Anon! Knew there was something missing. Good to know in general regarding VCE, too. In multisim it came out to 0.01 volts, very small.

[Anonymous No.11550072]

>>11547724
If you can increase the concentration of household bleach the sodium hypochlorite in it has a tendency to get a little on the exothermic side with gasoline

[Anonymous No.11550086]

>>11550053
Stop being a brainlet

[Anonymous No.11550093]

>>11550086
im trying

what are the limit rules I need to apply? obviously a^n/b^n = (a/b)^n, but im still not sure how to calc the limit

[Anonymous No.11550141]

>>11550093
It's like the first trick you learn.

[Anonymous No.11550142]

>>11550141
it's been awhile mang

[Anonymous No.11550155]

do alternating repeating decimals converge or diverge?

i would assume diverge but pls explain good enough for the prof

[Anonymous No.11550165]

>>11550155

fuck you bitch

[Anonymous No.11550169]

>>11550165
stahp im in a hurry, obviously it converges to the value of the repeatng decimal, but how do i express it as a sum of a ratio of integers?

[Anonymous No.11550172]

>>11550169

Neither you brainlet, a number is a number. The repeating portion simply shows how willing a human is to write out endless numbers.

2/3 = 2/3 no matter how many times you write .6666666666666666666666666666666666666666

[Anonymous No.11550175]

>>11550172
He did ask about alternating repeating numbers but yeah still fuck him

[Anonymous No.11550176]

>>11550155
so how's the take home calc 2 exam going

[Anonymous No.11550179]

>>11550175

The point is that a number is a number, it doesn't matter how we "write" it. Numbers are literally just a human way of describing the universe in terms we can understand. It doesn't mean they are perfect.

anon is probably cool but his teacher assigning that question should fuck off

[Anonymous No.11550180]

>>11550172
that's what i said, but how do i express it as a sum of a ratio of integers? the number is 6.54818181.., so to express it as a sum of a ratio of integers, I try:
[math]
6 + \frac{5}{10}+\frac{4}{10^2}+\sum_{n=1}^{\infty} 81\cdot10^{-3+2n}[/math]
but this feels wrong, and not what the prof wants. i joined late and i forgot a buncha shit, just have to survive the first round of deadlines then i can catch up

>>11550176
it's just homework

[Anonymous No.11550181]

>>11547647
looks like a typo to me. s is just the standard deviation of the sample and it's given as 3 minutes

[Anonymous No.11550196]

>>11542661
This actually works just fine, you fix (x_1,...,x_n), then \chi(t,x_1,...,x_n) is different then 0 only for t=f(x_1,...,x_n), hence \int\chi(t,x_1,...,x_n)dt=0. then you integrate that over R^n.

[Anonymous No.11550197]

>>11550180

dunno bruh the highest math i ever took was calc 2 and that was 10 years ago

but i make six figures for a cushy job

think about the real math

[Anonymous No.11550200]

if you scroll down to 'converting mixed recurrign decimals to fractions' i think this is what prof wants, getting there

>>11550197
i've self studied a lot I just forgot all this annoying crap, i wish i could just jump straight to analysis i hate this kinda math

[Anonymous No.11550203]

forgot link
http://www.nabla.hr/CO-SequAndSeries5.htm#Converting%20recurring%20decimals%20(infinite%20decimals)%20to%20fraction

[Anonymous No.11550209]

>>11550200

what career path are you looking towards?

[Anonymous No.11550212]

>>11550209
being a big brain badass

[Anonymous No.11550221]

>>11550212

k, doing what?

[Anonymous No.11550223]

>>11550221
your mom

[Anonymous No.11550225]

>>11540602
my man OP is posting some kenket as op image!

good taste in animal artists, my man.

[Anonymous No.11550226]

>>11550223

stupid nerd

[Anonymous No.11550239]

so i think the solution looks something liek this, but i fudged it up somewhere
[math]
5.237575... = \frac{523}{100}+ \frac{\frac{75}{10^4}}{1-\frac{1}{10^3}} = \frac{523}{100} + \frac{\frac{75}{10^4}}{\frac{999}{1000}} = \frac{523}{100} + \frac{75}{10^4}\cdot\frac{10^3}{999} = \frac{523}{100}+\frac{75}{9990} = \frac{523 \cdot 9990 + 75 \cdot 100}{9990 * 100} = poopoppoepeopeopo
[/math]

>>11550221
well mom I'm glad you asked. it'd be comfy to get into grad school, but it's not much using talking about my future when my inability to complete the problems in front of me will ruin any plans i have anyway.

[Anonymous No.11550252]

>>11550239

just a boomer looking out for you when the economy is imploding and unemployment is going nuclear

but whatever don't mind me

[Anonymous No.11550253]

why does google's calc say 75/99 terminates wtf this waste me like an hour

[Anonymous No.11550265]

i figured it out guys

but just to check, would this be a good answer to the following:
"Given the geometric series below, determine if they converge or not and, if they do, find theirexact sum as a ratio of integers in reduced form."
0.31717171717....

my answer:
it converges to:
[math]
\frac{314}{990}
[/math]

i only reall need the number right, since it is it's own sum of geometric series?

[Anonymous No.11550270]

given that this converges to 0, how would I go about finding it's 'exact sum as a ration of intgers in reduced form'?
[math]
\frac{(3 \cdot 5^{n-1})(-1^{n-1})}{2^{n-1}}
[/math]

[Anonymous No.11550274]

>>11550270
it' be 0/1 duh you freakin idiot

>t. me

[Anonymous No.11550296]

>>11550221
why do you wanna know? i don't really know i just like math and school + living is free,may as well get credentials

[Anonymous No.11550308]

>>11550296

because i'd like to give whatever advice i have to to help you out. i'm 32 and and have no problem helping out other tards on 4chan

[Anonymous No.11550316]

>>11550308
im reluctant bc it's just a tad hypocritical for me to say i wanna go into math while having trouble with calc II, but i don't feel this is representive of my skill, motive or anything like that. i really enjoy proof based maths, which is all math is after you get through calc. i just smashed into this course super last minute and i fucking suck at learning/focusing under pressing deadlines

[Anonymous No.11550764]

>>11549098
bump. am I misunderstanding the definition?

[Anonymous No.11550772]

>>11550142
protip: think about what happens to number between 0 and 1 when taken to the natural power. Fucking retard.

[Anonymous No.11550816]

Qualitative question.

This is "centrifugal energy" in a nucleus. So... is that just a QM analog of a potential from centripetal acceleration? I didn't even know forces of inertia are still relevant on such scales.

[Anonymous No.11551008]

what's the point of a "knot" in dog dicks?
what is it made of?
muscles, some kind of blood pockets?

[Anonymous No.11551023]

>>11540602

WHAT ABOUT MASKS?

People say to never reuse the same mask, but the virus doesn't live any more than about 18 hours tops on surfaces like metal, so if I reuse the mask after 18 h or more why is that a problem?

[Anonymous No.11551032]

>>11540602

Anybody can recommend an easy but comprehensible nuclear physics book?

[Anonymous No.11551076]

How did he find this?

[Anonymous No.11551277]

>>11550253
>why does google's calc say 75/99 terminates
Because you didn't take/listen to your numerics class and are now finally realizing that computers almost never do correct calculations.

[Anonymous No.11551308]

>>11548958
>python
Yes.
Python is actually used in academia and almost certainly knowing it will be useful. It has the relevant libraries for basically any area and is relatively easy to pick up.
A more "niche" alternatives would be julia, which is from a mathematical perspective is easier to use, but is generally less supported/known. Another alternative is Matlab, but I would try to avoid it if possible, although the language on its own isn't terrible...

>java or javascript
No. Avoid them.
JavaScript is almost exclusively meant for webdev and that really shows in the language, Java enforces a very particular style of programming which makes it very tedious to use for anything that doesn't intend to be some large scale application.

[Anonymous No.11551359]

whats the difference between Lorentz indices and spacetime indices?

[Anonymous No.11551515]

>>11551076
You know the direction and magnitude of tension in AB and AD. There is only one other force acting on A. Because it is in equilibrium, you know you the forces sum to zero. Graphically, however, this means you can arrange all the force vectors tail-to-tip to form a closed triangle. Use geometry and the law of cosines to find the angle and length of the third side. Parallelogram law is the same thing, if you look closely.
>>11551008
https://en.wikipedia.org/wiki/Canine_penis
>>11550265
Say you have a number less than 1 written in standard decimal form [math] q=0.a_1a_2a_3... [/math] where d1, d2, etc are integers [math]\in[0,9][/math]. We can see that q has non-terminating decimals. By definition this means [math]q=(a_1/10)+(a_2/100)+...=\sum_{n=1}^\infty a_n\cdot10^{-n} [/math]. If [math] a_1=a_2=...=a_n [/math] for all n then its easy to see this is a geometric series and using the classic formula for a geometric series you can get [math] q [/math] in the form of a fraction. It's also easy to see how this works if you have a set of m numbers that repeat in the sum like [math] a_1=a_r, a_2=a_{r+1},...,a_m=a_{r+m} [/math] for fixed r.
>>11549761
I think you might misunderstand. I meant use superposition just to get current, but that is really overkill. You can just sum voltage drops over the closed loop to get current. Then you have the complex power over each element. Don't use superposition, srry srry.

[Anonymous No.11551530]

>>11551076
You know the direction and magnitude of tension in AB and AD. There is only one other force acting on A. Because it is in equilibrium, you know the forces sum to zero. Graphically, this means you can arrange all the force vectors tail-to-tip to form a closed triangle. Use geometry and the law of cosines to find the angle and length of the third side. Parallelogram law is the same thing, if you look closely.
>>11551008
https://en.wikipedia.org/wiki/Canine_penis
>>11550265
Say you have a number less than 1 written in standard decimal form [math] q=0.a_1a_2a_3... [/math] where a1, a2, etc are integers [math]\in[0,9][/math]. We can see that q has non-terminating decimals. By definition this means [math]q=(a_1/10)+(a_2/100)+...=\sum_{n=1}^\infty a_n\cdot10^{-n} [/math]. If [math] a_1=a_2=...=a_n [/math] for all n then its easy to see this is a geometric series and using the classic formula for a geometric series you can get [math] q [/math] in the form of a fraction. It's easy to see how this works if you have a set of r numbers that repeat in the sum like [math] a_1=a_r, a_2=a_{r+1},... [/math] for fixed r.
>>11549761
I meant use superposition just to get current, but it is overkill. You can just sum voltage drops over the closed loop with all sources in place to get current. Then you have the complex power over each element. No need to combine powers after you compute them.

[Anonymous No.11551699]

what's this limit
[math]
\lim_{n \to \infty} \frac{(-1)^{n-1}2n(n+1)}{3n^2 + 2n - 4}
[/math]

[Anonymous No.11551704]

>>11551699
0, just like you're IQ.

[Anonymous No.11551710]

>>11540602
I have a stupid question.

How does a retard like me go from zero to world-changing Physicist?

Generally analytically minded. Kind of a NEET, want to go be productive. Granddad worked at NASA, would like to one-up that and do something bigger and better. (As in, he had teams of scientists under him and he'd tell them to solve whatever problem, they'd do so, and then he'd go about compiling the answer and getting it where it needs to go. Basically, the guy who'd answer the "Houston we have a problem" call.)

Don't know jackshit about physics or math for that matter.

[Anonymous No.11551712]

stupid question: the following inequality is true, right? [eqn]\left( \sum_{i=1}^n a_i b_i \right)^2 \leq \left( \sum_{i=1}^n a_i \right)^2[/eqn] if [math]|b_i| \leq 1[/math] for all [math]i[/math] ([math]a_i, b_i[/math] are all real numbers).

It just seems weird to me because Cauchy-Schwarz gives a very different bound, something like [eqn] n\sum_{i=1}^n a_i^2. [/eqn] I suppose which one is better depends on the [math]a_i[/math]'s?

[Anonymous No.11551724]

>>11551712
The inequality is wrong.
For example,
a_1=1
a_2=-1
b_1=1
b_2=-1

[Anonymous No.11551727]

>>11551704
that's what i thought, now if it was a series would it also converge to 0?

[Anonymous No.11551741]

>>11551724
Ah, derp. It should be [math]( \sum_i |a_i| )^2[/math], right?

[Anonymous No.11551815]

is the problems in pic related solved correctly?

[eqn]
\frac{0}{n^3} \leq \frac{sin(n) + 1}{n^2} \leq \frac{2}{n^3} \\
\lim \frac{0}{n^3} = 0, \lim \frac{2}{n^3} = 0
[/eqn]
So by squeeze theorem, [math]\frac{sin(n) + 1}{n^2}[/math] converges to 0.


I'm having a hard time distinguishing between the limit of the equation for the nth term in the series (in this case, pic related), and the limit of the sum, if that makes sense. sorry for the shitpost

[Anonymous No.11551822]

>>11549790
retard

[Anonymous No.11551830]

also, in relation to above, the question is to find out if the sequences converges or diverges, and if it converges, find the limit

[Anonymous No.11551832]

>>11540602

Where can I read about vibration and rotation energy levels in a nucleus?

[Anonymous No.11551851]

>>11551815
>>11551830
>I'm having a hard time distinguishing between the limit of the equation for the nth term in the series (in this case, pic related), and the limit of the sum
I don't see any sum anon.
And yes the term converge to 0.
If you are taken the sum of all [math]a_1[/math] to [math]a_n[/math], then it would still be 0 because the lim of the enumerator is [math]n[/math]. So lim of [math]n/n^3[/math] is 0.

[Anonymous No.11551864]

>>11551741
But then it's trivial.

[Anonymous No.11551865]

>>11551815
>>11551830
>>11551851
so just to make sure I'm getting it, since im being asked to find whether these sequences converge or diverge, and if they converge, find the limit, it is as simple as just taking the limit of each sequence formula, right?

so, again, in the case of pic related, since this sequence goes to zero as n goes to infinty, the answer is simply that it converges at 0?

[Anonymous No.11551884]

>>11551864
Well, I did warn that it was a stupid question.

[Anonymous No.11551885]

>>11551865
Yes.
If you are asked about
>Limit of the Sequence
https://en.wikipedia.org/wiki/Limit_of_a_sequence#Real_numbers
You only need to present the limit of [math]a_n[/math].
>Limit of the Series
https://en.wikipedia.org/wiki/Series_(mathematics)
In this case, you need to present the limit of [math]\sum a_n[/math].
Anyway, I'm not entirely sure if your pic related is converging to 0. It has been a while since the last time I did those. But yeah in this case you only need to find the lim of [math]a_n[/math].

[Anonymous No.11551922]

>>11551865
Also, a term in the sequence can actually be represented by a sum of a series, so don't be confused.
It can get deeper and deeper as in sum of series in which each term is a sum, etc.

[Anonymous No.11551968]

>currently in waves & heat
>doing great, 98 average for exams so far, explaining concepts to my peers when they have trouble
>also in circuits 2 currently
>struggling like the dickens with bode plots
its not fair bros

[Anonymous No.11551981]

>Schrodinger's cat
Why would a person observing the cat collapse the wave function? If i understand this correctly, the observer effect has more to do with measurements interfering with the particle than a conscious observer literally changing how reality works. Shouldn't the cat remain in a state of both dead/alive even after the box is opened?

[Anonymous No.11552030]

>>11551981
>a conscious observer literally changing how reality works
pretty sure thats what the quantum eraser experiment is

[Anonymous No.11552037]

>https://www.buckeyefirearms.org/alternate-look-handgun-stopping-power
This study suggest that the average number of rounds fired before a handgun engagement is ended, is 1.78.
I work in an industry where standard are sometimes set to six sigma, which translates to 2 defects per million oppurtunities.
What number of cartridges would somebody have to fire, untill it would cover all save 2 oppurtunities out of a million? In other words, how much ammo should one carry to cover six sigma of all defensive handgun scenarios?

With regards, from /k/.

[Anonymous No.11552061]

What do I need to know to make fat stacks of cash money?

[Anonymous No.11552073]

Any organic chemists here? what functional group is represented here? I think it might be something like a thioketone, thione, and/or thiocarbonyl? Im just not sure if the extra O and S come in to play.

[Anonymous No.11552076]

>>11552061
how to give good blowjobs

[Anonymous No.11552109]

>>11546881
someone just tell me something...im bored and want to study

[Anonymous No.11552130]

how do I go about solving this with the central limit theorem if I don't know the standard deviation for the population?

[Anonymous No.11552138]

>>11552073
it is a dithiocarbonate

[Anonymous No.11552146]

>>11550816
Ehrenfest's theorem states that expectations of observables satisfy classical laws of motion. Why did you think Coulomb stops working at the quantum scale? That's absurd.
>>11551359
None. Symmetry indices are indices corresponding to a representation space [math]V[/math] where [math]\pi: G\rightarrow GL(V)[/math]. For Lorentz [math]G[/math] happens to be the homogeneous isometries [math]\operatorname{Isom}^+ M \cong SO(1,3)[/math] of the tangent bundle [math]V = TM[/math].

[Anonymous No.11552179]

>>11552138
Thank you!

[Anonymous No.11552182]

>>11552146
Then i have no idea whats going on. I'm trying to study Gravity as a YM theory and got into tetrad fields. As far as i understand, we introduce these fields to have the ability to change between spacetime/world indices and Lorentz indices: [math] dy^{a} = e^{a} _{\mu} (x) dx^{\mu}[/math]. Of course one can define them from a different perspective using the spin structure but i'm a bit confused about the indices. Any help appreciated.

[Anonymous No.11552188]

>>11552037
Knowledge of the mean of a random variable is not sufficient to specify its standard deviation, even if you know it takes on only non-negative integer values. That said, a model as a Poisson random variable is plausible. You can look up tail probabilities for the Poisson distribution. I believe that with 10 rounds the probability of needing more is about 3 in a million, and with 11 rounds, less than 1 in a million.

[Anonymous No.11552242]

>>11551815
I think you meant
[eqn]\frac{0}{n^2} \leq \frac{\sin(n) + 1}{n^2} \leq \frac{2}{n^2}, ~~~\forall n \in \mathbb N[/eqn]
since [math]-1 \leq \sin(n) \leq 1[/math]. No need to change [math]n^2[/math] whatsoever -- in fact your bounds might even be incorrect for some [math]n[/math]. Other than that your application of the theorem is correct.

[Anonymous No.11552256]

>>11552182
A spin structure is an isomorphism [math]TM \xrightarrow{\sim} \operatorname{Cliff}(V)[/math] to a Clifford bundle; this means that every fibre in the tangent bundle [math]T_xM \cong V_x[/math] is (up to isomorphism) a representation space [math]V_x[/math] for a Clifford group, which captures the algebraic properties of spin. This endows [math]M[/math] with a spinor bundle [math]S \rightarrow M[/math].
The vierbeins [math]e[/math] form an orthogonal frame of [math]TM[/math], and the form of the metric tensor [math]g[/math] depends on this choice. The choice natural to the canonical frame [math]dx \in TM[/math] was picked out to be the "spacetime frame", while the above isomorphism [math]TM \cong \operatorname{Cliff}(V)[/math] rotates it into the "Lorentz frame"; the vierbeins [math]e[/math] implement this rotation: [math]g_{\mu\nu} = e_\mu^a e_\nu^b g_{ab}[/math]. This equation can be seen as a necessary consistency condition for the existence of a spin structure.
To see this, suppose [math]V[/math] is taken to be flat, then [math]e[/math] can be seen as a "square root" of the metric tensor, which defines a global section of a "square-root spin bundle" [math]\mathcal{S}[/math] for which [math]\mathcal{S}^{\otimes 2} \cong S[/math]. This implies that the obstruction class for spin structures, i.e. the characteristic second Stiefel-Whitney class [math]f^*w_2 \in H^2(M,\mathbb{Z}_2)[/math], where [math]f: M\rightarrow BSO(1,n)[/math] is the classifying map, vanishes.

[Anonymous No.11552272]

Could the moon be reflected like that and from what vantage point?

[Anonymous No.11552288]

>>11552256
ok this is a bit advanced for me, i'll look it up tho, thanks. Also shouldn't it be [math]dx \in T^*M[/math]?

[Anonymous No.11552296]

>>11552288
Yeah, but given a choice of a Riemannian metric they're isomorphic [math]TM \cong T^*M[/math] as each others' duals. This isn't canonical but me writing [math]TM\cong V[/math] isn't canonical either so whatever.

[Anonymous No.11552308]

>>11552296
okay cool. ty

[Anonymous No.11552312]

>>11551359
>Lorentz indices
Never heard of that

[Anonymous No.11552475]

>>11540604
>>11524877
yes lighting is just that powerful that it can ionise the air to reach its node.

In order to see which the lightining wil most likelyl hit, you have to see which offers the least path of resistance. the metal probably wins because it is so conductive, and can be polarised or charged to draw the lighting in to it as well.

[Anonymous No.11552483]

>>11552312
well, you have now

[Anonymous No.11552733]

>>11551865
>it is as simple as just taking the limit of each sequence formula, right?
Yes, if you are being asked for the limit of the sequence

[Anonymous No.11552777]

>>11552130
standard deviation is the square root of variance

[Anonymous No.11552783]

>>11549537
oh shit... it actually is...

[Anonymous No.11552825]

>>11552777
That's for the sample. I need it for the population

[Anonymous No.11552920]

I want to explore multiples and exponents. What are some good texts that introduce the fundamentals?

[Anonymous No.11552940]

how long did it take you to get fully comfortable with basic algebra?

[Anonymous No.11552966]

>>11552130
>>11552825
Central limit implies that in the limit n is big, usually greater than 30, you have it that [math] \sigma\approx s/\sqrt{n} [/math]. Here you've got [math] \nu=n-1=19 [/math]. From Student T you must find the confidence interval [math] c=1-\alpha [/math] such that [math] \mu-t_{\alpha,\nu}s/\sqrt{n}<\bar{x} [/math].
>>11552920
khan academy

[Anonymous No.11553075]

can someone help me determine if this converges and how to find it's sum?


[eqn]
\frac{3(5^{n-1})^{\frac{1}{2}}\cdot(-1)^{n-1}}{(n+1)!}
[/eqn]

[Anonymous No.11553081]

>>11553075
meant to say this is a series being summed,not a formula for partial sums

[Anonymous No.11553228]

>>11553075
>>11553081
ok, scratch that. help me determine if this converges:
[eqn]
\sum_{n=1}^{\infty} \frac{((5)^{n-1})^{\frac{1}{2}}}{2^{n-1}}
[/eqn]

[Anonymous No.11554143]

>>>11540602
Are There Prime (x) numbers That have this two Conditions:

prime(x) = (prime(y)* 2) +1
prime(z) = (prime(x) * 2) + 1

[polite sage No.11554777]

>>11541589
see >>11554771