/sqt/ Stupid Questions Thread

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symbolab.com/solver/power-series-calculator/\sum_{n=0}^{\infty} n!\left(x-1\right)^{n}
symbolab.com/solver/power-series-calculator/\sum_{n=0}^{\infty} \frac{\left(2x\right)^{n}}{\left(3n\right)!}
amazon.com/000-Solved-Problems-Linear-Algebra/dp/0070380236
amazon.com/Algebra-Problem-Dolciani-Mathematical-Expositions/dp/0883853221
wiki.c2.com/?RubberDucking
twitter.com/SFWRedditVideos

would it be possible to grow crystals of pyrite in a home lab?

I've seen people grow those copper pentahydrate crystals at home and thought it would be cool to try and grow pyrite (iron sulfide) from a solution with a seed crystal. I'd expect the pyrite crystal to be a perfect cube, like in the picture.

I'd like to learn about continued fractions. What concepts should I have under my belt and through which texts should I work?

>What concepts should I have under my belt and through which texts should I work?
I don't think you really need any particular knowledge beforehand, but try chapter 7 of pic related

what happens if i get a 0 or infinity for the radius of convergence for a power series? what do i write as the answer to the problem?

>what happens if i get a 0 or infinity for the radius of convergence for a power series? what do i write as the answer to the problem?
0 or infinity, respectfully

do i put that as the answer if the question is asking for the interval of convergence and not the radius?

0 = series converges nowhere
inf = series converges everywhere

that's what i was thinking too but symbolab is telling me that if the radius is 0 then the series converges everywhere and if it's infinity then the series converges at only one point

symbolab.com/solver/power-series-calculator/\sum_{n=0}^{\infty} n!\left(x-1\right)^{n}

symbolab.com/solver/power-series-calculator/\sum_{n=0}^{\infty} \frac{\left(2x\right)^{n}}{\left(3n\right)!}

For that first one doesn't it say that it diverges for all x not 1? And then say it's a radius of 0?

oh yeah it does say that. i was thinking that the answer to the ratio test was the radius of convergence which was infinity.

...

There was a study on policy positions of americans and it mentioned 58% of latinos felt a certain way and 68% of black people felt another way, but omitted white opinion.
How do I find the missing percentage? I don't need a precise answer and asians and other races are negligible.

Anyone know of good exercise material for linear algebra? I'm a dumb fuck that's trying to (re)learn fundamental maths stuff, and I'd like to spend some time each day doing exercises on the things I learn. I jewgled for this stuff but it was mostly million page PDFs that were way over my head. I just want something where it gives me N instances of X problem to solve, repetition is key and whatnot.

Schaum's is good for that.
3,000 Solved Problems in Linear Algebra
amazon.com/000-Solved-Problems-Linear-Algebra/dp/0070380236

I took an Edx math course. I don't know if the one I took is still there but it had an interactive system sponsored by some college that introduced every concept with randomly generated problems in an order and would reintroduce concepts after a period of time.

I've heard it said that energy is quantized because of E=hf, but wouldn't it make more sense to say that frequency is quantized instead?
Esprcially since mass is continuous (afaik) and mass-energy equivalence is a thing.

...

Total energy is quantized in many situations with a potential (e.g. hydrogen atom, quantum harmonic oscillator), since there are discrete energy levels the particle can be at.

amazon.com/Algebra-Problem-Dolciani-Mathematical-Expositions/dp/0883853221

True, I guess what I'm really asking is for a satisfying interpretation of the energy-momentum relation (E^2 being the sum of a discrete and a continuous term seems to me like trying to add different types of things, though it's probably because I have no formal training in phyaics).

i made a B in physics 1 although I literally just plugged values randomly into equations i was given and hoped for the best. i made As in calc 1 - calc 3 so i swear im not a brainlet. i basically just cannot for the life of me understand torque and tension and rotational acceleration and momentum and friction. stuff like the ladder problem, my brain shuts down.

how will this come back to haunt me in physics 2 if at all?

(sage for mathematical masturbation and phoneposting, though I wouldn't mind knowing if there are sensible.interpretations for what I'm doing)

Maybe frequency f = c/lambda is discrete but the (imaginary) angular frequency w = 2pi*i*f makes it continuous, which allows pc = i*hbar*w to be meaningfully added to a continuous term.

The relation [math]p^2 + m^2 = 0[/math] is called the "on-shell" relation, which means that only physical momenta satisfy these relations, while the energy quantization relation holds for particles. The "continuous" 4-momenta (which includes the energy [math]E = p_0[/math]) are attached to vertices of the Feynman diagrams arising from fields lying in the closure of the net of local observable algebras under the weak operator topology [math]\mathcal{A} = \operatorname{cl}\left(\bigcup_{U \subset \mathbb{M}} \overline{\mathcal{A}}(U)\right)[/math], while the "discrete" energy is assigned to the particle counterpart of these fields, namely the excitations on the states in the GNS Hilbert space [math]\mathcal{H} =
\bigwedge_i \mathcal{H}_i/\{\Psi \in \mathcal{H}_i \mid \langle \Psi|\Psi\rangle \leq
0\}[/math] (or, for free fields, the Fock space [math]\mathcal{F}[/math]). So the "continuous" notion of energy is associated only with the coordinates of the fields, which are operator-valued distributions on the symplectic vector space [math](\mathbb{M}^2,dp^\mu dq_\mu)[/math] while the "discrete" notion of energy is associated with the eigenvalues of the Hamiltonian operator on states [math]\Psi \in\mathcal{H}[/math]. These are in essence two different things, and technically only the "discrete" energy is observable.
I hope this clears up any misunderstanding.

>would it be possible to grow crystals of pyrite in a home lab?

>i swear im not a brainlet
>stuff like the ladder problem melts my brain

>wouldn't it make more sense to say that frequency is quantisized instead?

what grades did you make in calc 1, 2, and 3?

physics 2 is more about electricity and not mechanics so you're good

I haven't ever been to college. I'm 18 and barely old enough to post. I understand roughly 1/7 of the conversations on this board, and that's thanks to retards talking about global warming and Veeky Forums shit leaking over, which I can understand. I love posting retard faces, of which I have more than fifty, especially in stupid questions threads.

>I hope this clears up any misunderstanding
I'd be lying if I said I understood enough of that to clear up *all* misunderstandings, but from what I could glean it seems that the discrete-continuous dichotomy essentially boils down to doing physics in function space vs physical space, and manifests as 'wave-particle duality'.
Which is about as far as I can go given my current level of knowledge really.

Can I scientifically prove the existence of numbers?

Rephrasing the question, can the existence of numbers be proven by science or it is an abstract object that the existence is accepted based in the "certainty" that they exist?

I don't think so, but you can prove the existence of numerals.

It is sensible to interpret it that way, though I'd say that they're entirely distinct things, just named similarly. The mathematical statement of particle-wave duality is the existence of a unitary morphism taking boson fields [math](\Gamma,A,\omega,v_0)[/math] to an [math]N[/math]-particle Fock space [math]F[/math] that maps the vacuum field [math]v_0\in\Gamma[/math] to the cyclic vacuum state [math]|0\rangle[/math] in the Fock space. Since this statement doesn't directly concern energies I'd be hard-pressed to say that the continuous/discrete dichotomy is due to particle-wave duality.

would a gun shooting a 200 grain bullet have twice as much recoil as the same gun shooting a 100 grain bullet with the same charge?

I jack off to 2hu and have an interest in math.
How do I access my pineal gland to unleash the massive levels of 2hu math autism as you have consistenly shown through the last few months.

Just bee yourself user.

any pro tips or guides?
who is your favorite 2hu?
Where do I start to unlock your subterranean autism?


[math] \textrm{ which touhou h-doujins do you prefer }[/math]

can i multiply together 2 numbers with a variable as an exponent or do i need to leave them separate? example:
[math](-1)^n (-2)^n[/math]

it depends on what n is

for example
1 =
(1)^(1/2) !=
(-1)^(1/2)(-1)^(1/2) =
i*i =
-1

>any pro tips or guides?
Can't tell you since I've never used any.
>who is your favorite 2hu?
Ran is qt.
>Where do I start to unlock your subterranean autism?
Get one of those IQ increasing drugs from Eirin or something lmao.
>[math]\mathfrak{which}~\mathfrak{ touhou}~\mathfrak{ h}-\mathfrak{doujins}~\mathfrak{ do}~\mathfrak{ you}~\mathfrak{ prefer}[/math]
I liked the one where Yukari and Yuyuko raped this one village boy.

i'm trying to test pic related for convergence and i don't know if i need to simplify this further or just do the alternating series test on it or something as-is

it is true for integers n, so you can simplify that to n^2

so it would simplify to pic related and then cancel?

>respectfully

>so it would simplify to pic related and then cancel?
yep

cool thanks

this brainlet meme is getting out of hand

well, at least you're honest. good luck when you make it to college. this stuff ain't easy.

You're very honest. Your honesty will be used against you soon.

Can / will you teach / tutor me?

[math] \frak{do\ you\ enjoy\ spacejin\ ?} [/math]

>not paying your respects to math
t. brainlet

The Veeky Forums I know and love

he's just a kid out of high school posting pictures he thinks are funny. there's no malice behind his posts. i'm one of the guys he replied but i have no desire to poke fun at him. he's probably a nice dude irl.

>Can / will you teach / tutor me?
How much are you paying me?
And no I fucking hate spacejin.

[math] \textrm{I don't have a disposable income. Do you accept nudes, 2hu doujins, or have anything else you need? I can be your best friend! (I am a worthless NEET---go figure).} [/math]

why are you trying to learn extremely niche math concepts as a NEET? get an engineering degree and you'll be swimming in dosh. this high level math is pointless to learn. there's no reason outside of academic settings to know it.

I have a Bsc. in physics from a garbage SJW university. I met some people along the way that did dynamics, chaos, and dynamical systems in neuroscience (this one fucking russian autist professor can do math like no other, he is my spirit animal). I just look up to them as a brainlet naturally would. Seeing 2hu and real math (I.E. topology, sets, real linear algebra) made me remember how happy I was in college. I also am a lonely NEET who wants to jack off to 2hu NTR doujins with someone else.

look user, instead of trying to find a jack off buddy you can hot glue a fumo with, why don't you try to find a job instead or at the very least get a more marketable degree?

maslow's heirarchy, user. get a job and meet that basic need. then , if you must, be a degenerate.

I might be a navy officer in Feb. of next year.

[math] \frak{can\ we\ at\ least\ be\ fap\ buddies} [/math]

>I also am a lonely NEET who wants to jack off to 2hu NTR doujins with someone else.
You fucking sick fuck

>wants to join the navy
>also wants to find a dude to jack off with
like pottery

Not gay just lonely. But I am glad you could get some entertainment.

Were all lonely autists, this is Veeky Forums after all

Just. Not all of us want to mutually masturbate with a jper

I didn't quite literally mean circlejerking. I know you understood what I meant since I am acoustic/statistic.

Anyone have an idea of how I would find a parametric equation to fit this curve. Pic is all information I was given.

Why is the notation of second order derivative like d^2/dx^2?
Why not d^2/d^2x?

when you take high order partial derivatives of multivariable functions you want it to be clear how many times you take a derivative of each variable i.e.
[math] \frac{\partial^3}{\partial y^2 \partial x} [/math]

Say $f: A \rightarrow B$, does $f ^{-1}$ necessarily have to be a function?

d(dy/dx)/dx = d^2y/dx^2

if f^(-1) denotes the general pre-image, then no. if it's being used to denote the inverse function then by definition yes it's a function

fucked up my latex:
Say
[math]f: A\rightarrow B [/math], does [math]f^{-1}[/math] need to be a function, or can it just be a relation

thanks!

Which is more fundamental: logic, or the natural numbers?

Logic, obviously.

How do I solve the laplace transform of Piecewise[{{Sin[t], Sin[t] > 0}}, 0] ?
WolframAlpha gives e^(π s)/((e^(π s) - 1) (s^2 + 1)).

I tried verifying it by hand using the integral formula for periodic functions with f(t) = Sin(t) - Sin(t) * UnitStep(t- Pi) and with period T=2pi, but this gives a slightly different answer of e^(π s)/((e^(2 * π s) - 1) (s^2 + 1)). Why would the period be pi, not 2pi? I understand the integral can be simplified by interpreting 1 - UnitStep[t-pi] as halving the upper limit, but why would the denominator e ^ (sT) also change?

That's also what I would have said going by intuition, until I started writing up their definitions:

>Natural numbers
0 is a natural number.
The successor of a natural number is a natural number.
(All subsequent operations can be defined in terms of these, qua Peano)

>Logic
Absurdum is a proposition.
For any two propositions A and B, the implication "if A, then B" is a proposition.
(All subsequent operations can be defined in terms of these.
Using NAND alone doesn't work since you still need to assume the existence of at least one proposition P for the theory to be semantically non-vacuous.)

Or maybe this just means that the natural numbers are syntactically more fundamental (they're representable as tally marks, while you need parentheses for propositional logic as it has non-associative operators) while logic is semantically more fundamental (your domain of discourse only needs two values, qua Suszko, rather than infinitely many of them).
Unfortunately this is imprecise since I don't actually have a working definition of what it means to be "fundamental" (and I suspect that such a definition, if it existed, won't turn out to be fundamental at all).

nevermind, made a typo, and turns out to be the same thing after simplifying because of periodicity of e ^ z.

In terms of vector arithmetic, for an equation like:
4u-3v
would v be multiplied by 3 or -3?

What's the deal with the zero point energy field?
How can the vacuum be filled with energy?

they're the same thing because (-v) = (-1)v in vector spaces
proof literally trivial

proof literally trivial

Fuck I think I might be retarded, studying differential equations and the book says:
dy/dt = ay - b -> (dy/dt)/(y - b/a)

I don't understand how they get that, at most I can do (lets say dy/dt = x because I'm lazy):
x = ay - b -> x = (ay - b)/a -> x = (y - b/a) -> x/(y - b/a) = 1

I also just realized while writing this that I am retarded and somehow forgot that if I'm going to divide the right side by a, I have to divide the left side too (which then results in the correct equation). I am still posting this because I'm a fucking retard who deserves the shame.

>I also just realized while writing this that I am retarded and somehow forgot that if I'm going to divide the right side by a, I have to divide the left side too (which then results in the correct equation).
This phenomenon actually happens more often than you think, to the point that it's acquired the name of "rubber duck debugging".
wiki.c2.com/?RubberDucking probably explains it better than I can.

>dy/dt = ay - b -> (dy/dt)/(y - b/a)
What the fuck is that supposed to mean?

>lets say dy/dt = x
ever heard of y' ?

if you can make a vector u from a linear combination of vectors v and w, does that mean that u belongs to the span of vectors (v, w)?

If a large asteroid were to hit the moon today (think of the asteroid that made the Copernicus or Tycho crater), would you hear the impact from Earth or would it be silent?

Would you hear any sound from outside Earth if
it was loud enough and came from close enough?

That's kinda why I ask, 75% of the time I come up with the answer while typing the question myself. Second best way to learn, after trying to teach the stuff to others.

>What the fuck is that supposed to mean?
That's me forgetting the = a at the end.

>ever heard of y' ?
Good point but that's 2 key presses, a whole 100% increase over x.

No, sound waves require a medium to travel through, so they can't travel through space.

yeah man

I have a AxAx1xN array in matlab I wanna save for later, is there a format/method for saving it so that the AxAx1xN structure to it is preserved other than just writing it as a AxAN csv file and reshaping it myself after importing?

Nevermind I got it, shoulda just saved them as the variable it already is, thanks Matlab

why the fuck is
x^2+x+1 / x^2+x+2
NOT
1/2

Because 1/2 doesn't equal x^2+2x+2+x^(-2)

If my wife and I are sex addicts would this affect a baby in utero? Can you have too much sex, even without penetration?

yes you could get the baby pregnant if you penetrate too far

Does listening to a lecture with only one headphone in one ear any different than with headphones in both ears? If so does it matter which side?

is three fourths a half?

you can't cancel out the x's unless you can factor them out and you cant factor them out because the 1 and 2 don't have an x

But the pre-image is a function from B to the powerset of A :)