/sci/ - Science & Math

>really fucking long
Update: tallying on my phone in fucking warosu is impossible, I'm doing it once I get home in ~5 hours.

Which scientific startup would you open with 50,000,000$?

what's the scientific reason for sisters kissing eachother being so hot?

I got fucked this term by my first proof-based class. I want to practice some more since I'd rather believe it was difficult because I fell behind rather than come to terms with my brainletism. Does anyone have a good set of practice proof problems? If relevant, we got up to constructing the real numbers.

I don't think you're going to be able to link to a deleted thread, anon. It's actually impressive how much jannies hate me.

>>11235389
I gotchu babe. It's actually incredible how much jannies hate me.

Unanswered questions from the previous thread:
Math questions:
>>11225711
>>11234121 (Something something deform the multiplicative structure of a field equipped with an elliptic curve.)
>>11234520

Physics questions:
>>11229069
>>11231303
>>11232589
>>11233427

Engineering questions:
>>11231732
Stupid questions:
>>11227717
>>11231886
>>11232589
>>11233162
>>11233335, further contextualized by >>11233422
>>11233688
>>11234105
LATE
AS
FUCK

>>11235770
ya beat me

>>11235770
and >>11231732 is an economics question, I'm 80% sure

>>11235794
Are you sure it's not a question about sponges or sponge-like material absorbing a fluid, i.e. water?

>>11235831
I am pretty sure it isn't.
https://www.investopedia.com/terms/a/absorption-rate.asp
https://en.m.wikipedia.org/wiki/Absorptive_capacity

If he is talking about sponges, then the relationship is just the conservation of mass.

>>11235837
>Absorption rate is a term most commonly used in the real estate market to evaluate the rate at which available homes are sold in a specific market during a given time period.
>absorptive capacity has been defined as "a firm's ability to recognize the value of new information, assimilate it, and apply it to commercial ends"
Those two don't really have anything to do with each other, tho.
If you're talking about how many houses will be absorbed, that's an extremely complex problem.

>If he is talking about sponges, then the relationship is just the conservation of mass.
No, more something like "if a sponge has instantaneous absorption velocity of 5 liters per second, how many liters can it still absorb".
Although the surface area should also factor in somewhere.

>>11235852
Okay. He might be talking about sponges. Absorptive capacity is a function of porosity, then. Anon should look at Darcy's Law and into hydraulic conductivity.

>>11235344
Why the fuck did the jannies kill the last /sqt/?

Where did I fuck up?

>>11235997
Ignore the duped 39,36 in the last line, that was a brain fart. It's supposed to be
>438,48-399,12 = 39,36

What program do you use for xy-plots?

>>11235997
you didnt apply barrows rule correctly.

>>11235997
What exactly are you trying to do? Dull pencil on gray graph paper hurts my eyes. Can you share the problem promt? Use TeX

>>11235982
Conjecture A: Jannies dislike Judyposter for the same reasons they dislike Yukariposter, namely being homosexual (specifically being interested in men, wouldn't know the finicky stuff), calling people honey and posting slightly lewd images sometimes.
The evidence that corroborates this is Yukarianon's posts vanishing every now and then.
Conjectue B: They also dislike him for the furry stuff.
Conjecture C: The jannies really like Touhou, and were becoming progressively more annoyed at Judyposter for making these threads.

If I had to guess, I'd go with B.
>>11236010
Plotting functions?
Desmos is nice.
You can also try SageMath.

>>11236031
>refers to a bunch of people as [anime character]-poster
>never dawns on him that the reason might be avatarfagging

>>11236034
But anon, my posts don't vanish.
No, seriously, go through the previous thread in the archive. Go through the last few dozen.
Plus, judyposter barely posts Judy nowadays.

>>11235982
Definately homophobic jannies. I'm strictly innocent and I would never avatarfag or post anthros or a bunny from a popular 2016 animated film.
>>11236010
MATLAB is extremely easy to use if you want to plot functions of a single variable. Use Octave if you are poorfag or like opensource software. Or you can use Desmos. Who cares.
>>11236016
This is the first time I've ever heard of Barrow's rule. I'm curious: how is this different from the fundamental theorem of calc? Is this a European thing?
>>11236031
You understand me~
>>11236034
Remelianon is not the one who jannies love (hate) so much.

>>11236036
judy is banned on sight these days.
>1 day ban, off topic

>>11236041
That's fucking rough.

>>11235344
How do you rank the /sqt/ avatarposters ?

Its probably Yukari > Judy > Remilia in terms of knowledge, but Judy >Remilia > Yukari in terms of being capable to post useful answers

>>11236119
oh, and Remilia > Yukari > Judy in terms who I would like to hang out with

Mathlet here, what is the purpose of determinants in LA? I've read lots of criticism towards Axler and I'm wondering what's all the fuss about.

>>11236119
havent been on here in a while so i cant readily recall who's who. that being said the one who starts referencing vector fields and manifolds whenever someone asks a calc 1 level question is by far the worst

>>11236532
retard

>>11236487
A determinant does two things:
>it tells you the n-dimensional volume of the n-dimensional parallelogram associated to the matrix's collumns
>the volume only zeroes when we can squeeze the parallelogram inside a hyperplane, so it also tells you when the matrix doesn't inject
>because det(A)det(B)=det(AB), it tells you how the linear transformation changes volume
Sheldon Axler, the pedagogical genius of our time, grasped two fundamental facts:
>determinants are an extremely intuitive and useful geometric concept, but hard to motivate algebraically
>the average student struggles with geometry like fish struggles with breathing air
So he wrote up a paper, which can be read here: https://www.maa.org/programs/maa-awards/writing-awards/down-with-determinants
which uses algebraic arguments about factoring polynomials and the like to prove classical results in linear algebra and has amazing quotations, such as
>We'll define the determinant of a matrix to be the product of its eigenvalues (counting multiplicities). This easy-to-remember definition leads to the usual formulas for computing determinants.
>>11236532
But anon, it's absolutely hilarious.

>>11236716
I understand now. People are triggered by Axler's approach because it's "brainlet"-tier in comparison with the classical approach, right? I didn't know you could define the determinant of a matrix with eigenvalues, that's interesting. Thanks.

A differential equation is a function expressed using one or more of its derivatives.
Find a solution to a differential equation essentially boils down to finding (or otherwise expressing) the original function.
How then does solving a differential equation differ from integration/antidifferentiating?

>>11236795
Because differential equations in general cannot be solved simply by antidifferentiating. Take [math] \ddot{x}+\dot{x}+x=\sin t [/math]
for example.

I'm reading this paper on Li abundances in stars, and I'm pretty sure I understand what's going on until they mention "Lithium residuals". I don't know what "Element residual" means in the context of spectrums and astronomy, so I don't know what the fuck I'm looking at in this plot

https://arxiv.org/abs/1903.02735

Can I use group theory to study electronic circuits? I'm brainlet-tier on higher maths, but I realized that transposing components in say, an RC circuit wouldn't actually change the behavior of the circuit. There'd be 3 components you'd be able to switch around: battery, resistor, and capacitor in an RC circuit so I assume you could relate it to S(3). Are there any cool things I can do with this information?

I think I get the intuitive idea of the material derivative, and I get how the definition is derived from the chain rule. But I don't get the final step in this derivation of the "balance in momentum equation" (see pic related).
The RHS of equation (BM1) is simply the total forces acting on a parcel of liquid, but on the LHS, why is the acceleration the material derivative of u (Du/Dt) and NOT just the regular derivative (du/dt)?

At time t, if I am concentrating on the force acting at point (x, y, z), then I am concerned with the acceleration of the fluid at point (x,y, z) at time t, and how is that not just du / dt?

>>11235344
i asked this question on math stack exchange a while ago and nobody answered: https://math.stackexchange.com/questions/3436221/fz-0-z-1-z-2-0-rightarrow-f-alpha-z-0-alpha-z-1-alpha-z-2-0-fora
intuitively it's pretty clear that the only way that it would maintain the same zero locus is if all the whole result is multiplied by the same term, and then the only way that could happen uniformly is if the polynomial is homogenous, because otherwise the terms could have different powers of the constant. is that good enough for a proof or am i a brainlet?

Will science yield a legitimate cure for homosexuality and gender dysphoria in the next few years?
Asking for a friend.

is it true you shouldn't eat a few hours before an exam so you increase ghrelin production or something

>>11236882
First, forget momentum and Newton's law and let's just think about kinematics and why we use the material derivative. Suppose you have a streamline in [math] \mathbb{R}^3 [/math]. By definition of streamline, this is the path fluid takes in space and is tangent everywhere to the velocity of the fluid at that point. At every point along that streamline, let's suppose the fluid has some arbitrary vector quantity, say [math] \mathbf{B} [/math]. Notice that if you change position along the streamline a tiny little bit, the quantity [math] \mathbf{B} [/math] will change a corresponding tiny little bit. Likewise if you increment time a tiny bit. This means [math] \text{d}\mathbf{B} [/math] is an EXACT differential. Now think of a small differential volume (like a cube, dxdydx) somewhere on the streamline. If [math] \mathbf{B} [/math] is a function of time as well as space, then the change in [math] \mathbf{B} [/math] will depend not only on the size of the cube but also the velocity through the cube. It is a mathematical property of exact differentials that we can hence write

[eqn] \text{d}\mathbf{B}=\frac{\partial \mathbf{B}}{\partial t}\text{d}t+\frac{\partial x}{\partial t}\frac{\partial\mathbf{B}}{\partial x}\text{d}t+\frac{\partial y}{\partial t}\frac{\partial\mathbf{B}}{\partial y}\text{d}t+\frac{\partial z}{\partial t}\frac{\partial\mathbf{B}}{\partial z}\text{d}t [/eqn]

Now, divide by dt and use the definitions of the velocity vector and the gradient to write

[eqn] \frac{\text{d}\mathbf{B}}{\text{d}t}=\frac{\partial \mathbf{B}}{\partial t}+\mathbf{u}\cdot\nabla\mathbf{B} [/eqn]

(To be cont)

>>11236882
>>11237205
(2)

Therefore, along a STREAMLINE, the time derivative operator is

[eqn] \frac{\text{d}}{\text{d}t}=\frac{\text{D}}{\text{D}t}=\frac{\partial}{\partial t}+\mathbf{u}\cdot\nabla [/eqn]
Now, the d/dt notation and D/Dt notation technically mean the same thing, but fluid mech authors often choose the latter to remind you that you are talking about the derivative along a STREAMLINE. So, if you are talking about the momentum along a STREAMLINE, you must use the material derivative. What you have in your pic is the Euler equation of fluid motion, or the momentum equation for inviscid flow. Your text should derive that. But hopefully now you know why you use that material derivative operator.

>>11237077
Just be happy with being gay, m8. It aint gonna change. Don't let people bully you.
>disphoria
See a therapist maybe? I have very, very dysphoric trans friends and also trans friends who feel significantly happier and little stress when presenting as their authentic gender.

I'm taking 150MG venlafaxine (effexor in US I think).
I want to stop taking it but not cold turkey.
Can I open up the capsules, remove a bit of the thingy inside it and put the capsule back together?

Is there some sort of criteria on when to use the chemical element's name (say, Neon) and the symbol (Ne) when writing something? Or is it up to my mood?

If I were to throw a $5 Deep! Deep! Dish Pizza plus a 20-ounce bottled drink from Little Ceasers™ at 50 mph how much time would I have to walk to the nearest decent pizza place before the $5 Deep! Deep! Dish Pizza plus a 20-ounce bottled drink from Little Ceasers™ hit something?

>>11236931
no need for induction as I see it, the lemma you give is sufficient if you also consider that a homogeneous polynomial necessarily is composed of terms of equal total degree (sum of the degrees of variables in the term)

pls explain

>>11237444
Context? What is P?

>>11237455
Y ~ Poisson(4) | P(Y=4)

is the only bit before. When I do the sum I get an answer of 4000 something so I don't even know what is happening mathematically.

>>11237205
>>11237217
thanks that helps a lot

>>11236931
Something something consider the polynomial's term of highest degree h(x) and the remainder f(x)-h(x)=r(x), where we use x to denote the triple just because.
Either h(x)=r(x)=0 at all points where f(x)=0, or h(x)=r(x)=a=/=0 somewhere.
If the first, you remove common factors as usual, and consider the other case.
If the latter, fix x and consider the polynomial in the variable a p(a)=h(ax)-r(ax), where a multiplies pointwise yada yada.
Then p(a) has some number of zeroes, and if one of them falls out of the point 0, we're done by contradiction, and if it has a zero of multiplicity n at zero, we're also done, because it's homogenous.

Filling in the gaps is left as an exercise for the reader.

>>11237444
Looks like a latex typo. Think it should be:
[math]P(Y=4) = \frac{4^4}{4!}e^{-4} = 0.1953668[/math]
Correct Poisson distribution is [math]P(X=k) = \frac{\mu^k}{k!}e^{-\mu}[/math]

>>11237999
that makes sense, thanks

>>11235344
Hola nerds, physics student here hoping someone can help with clarification with some basic discrete math notation that I'm seeing in a comp sci context:

[eqn]\{0,1\}^*=\cup_{n\geq0}\{0,1\}^n[/eqn]

The union with a subscript is the bit I'm not totally comfortable with. {0,1}^* is the set of all strings of 1s and 0s of all possible lengths and {0,1}^n is the set of all strings of 1s/0s of length n

>>11238245
Its the union of all the sets where n >= 0.
[math]\cup_{n\geq0}\{0,1\}^n = \{0,1\}^0 \cup \{0,1\}^1 \cup \{0,1\}^2 \cup \dots = \cup_{n=0}^{\infty}\{0,1\}^n [/math]

I get Markovnikov's rule about alkene and alkyne reductions, but what of when both elements of the insaturated bond have the same number of hydrogens? For example, when trying to hydrogenate the double bond in pent-2-ene, is there some other rule as to which side will get the hydrogen and which one will get the x from Hx, or is it all down to the catalyst?

>>11237222
Yes you could. One of the most fundamental problems in pharmacy is making sure that medicine is as uniform as possible across an entire batch. It would suck if a single pill of your month-worth bottle of heart medication had all the actual active principle and all the rest were duds, wouldn't it? At any rate, of course, you shouldn't start or stop taking meds without informing your doctor. Are you on any other meds for the same reason? Because if you have depression, you really don't want to go any length of time without any medication in your system.

>>11237077
Homosexuality is a social construct. A bit of a cliche, I know, but them's the breaks. You don't "cure" people of their homosexuality so much as cure society at large of homophobia, which is the actual pathology.

>>11238262
Thank you anon, that makes sense. Have a favourite image of mine

>>11235450
If batteries and resistors and capacitors are elements of the group, would would the group operator be? What is R*C or V*C? How do you distinguish a parallel topology from a series?

>>11235427
It's known as μ-dick.

>>11236881
I'm familiar with circuits, but I confess I don't know about group theory. That said, it seems you might have stumbled upon something.

https://ieeexplore.ieee.org/document/1466509

What the fuck is the derivative with respect to gamma
[eqn]\log\left(\frac{n}{\sum_{i=1}^nx_i^{-\gamma}}\right)[/eqn]

I have tried to different ways and got 2 different answers since I am stupid as fuck, if I rewrite it as [math]n\log(n)-n\log(\sum_{i=1}^nx_i^{-\gamma})[/math] then I get that the derivative is [eqn]-n \frac{\sum_{i=1}^nx_i^{-\gamma}\log(x_i)}{\sum_{i=1}^nx_i^{-\gamma}}[/eqn] and if I don't I get [eqn]\sum_{i=1}^nx_i^{-\gamma}\sum_{i=1}^nx_i^{-\gamma}log(x_i)[/eqn]

>>11238310
>ieee
But does that apply to RC circuits?

>>11238322
Shouldn't you be rewriting it as [math] \log(n)-\log(\sum_{i=1}^nx_i^{-\gamma}) [/math] ?

Requesting a quick rundown on HP calculators.
Someone locally has an HP-49g plus listed for $80 CAD. I would love the SD card slot for writing large programs on PC and then transferring them over.
Are they good calculators?

Is there a series expansion of [math]x^x[/math] in infinity? It should grow faster than [math]x^n e^x[/math] but slower than [math]e^x^\alpha[/math] for any alpha bigger than one.

Can someone solve b) ?

>>11238498
Ich sprache keine deutsch.

>>11238760
What are you not understanding? It should be a simple calculation.

>>11238808
>>11238760
Last sentence describes the task:
Find a presentation of the following Form: "v3=v+.... "

Say I want to figure if this thing converges or not, would it be valid to say that this series is equivalent to 1/2n which diverges because it's the harmonic series divided by 2 and therefore the original one also diverges? If not, how would I do it?

>>11238498
>>11238808
>>11238817
First, we'll consider [math]l : \mathbb{R}^4 \rightarrow R[/math] defined by returning the sum of the coefficients.
So [math]V_1= \{v \in \mathbb{R}^4 such that l(v)=1[/math].
l(v) has some nice properties that make it a linear functional. This means that [math]l(u+v)=l(u)+l(v)[/math] and [math]l( \lambda u)= \lambda l(u)[/math].
Start by finding v. So you have that the outside element in [math]V_2[/math] has l(v)=1+2+3+4=10, so you need to pick an element of the generated subspace with l(u)=-9 by manipulating the above properties.
Then, you consider combinations of the [math]V_2[/math] subspace's generators with l(u)=0. Find two, and you're finished.
>>11238876
>the harmonic series divied by two
*Half the sum of the harmonic series.

Either all the n that get in the sum are even or odd. I'm not fiddling with powers to find out. If they're even, pass a two backwards and compare with harmonic. If they're odd, compare with the even (i.e. 1/n>1/(n+1) )part of the sum and apply above.

>>11238898
Based thanks :)

literature major here
does potential energy actually exist or is it an abstraction

>>11238921
All "energy" is an abstraction. But it still "exists" in the sense that it allows us to predict the evolution of a system. Potential energy is just as real as kinetic energy or thermal energy or energy stored in an electromagnetic field, etc.

>>11238876
Yes that's totally valid.

>>11235344
I've arrived at several sequence of numbers, by a process which is too convoluted to describe here. The first three sequences are related to mod 8, and possibly to the prime numbers 7, 11, and 13, respectively. The fourth sequence is related to mod 48, and possibly to the prime number 11. Can anyone identify any patterns in these?

mod 8 sequence:
>3, 4, 7, 4, 7, 4, 7, 4
>5, 2, 4, 6, 3, 6, 4, 2
>7, 5, 6, 7, 5, 7, 6, 7

mod 48 sequence:
>3, 26, 5, 10, 5, 11, 15, 4, 16, 10, 5, 9, 15, 16, 5, 15, 10, 5, 15, 11, 14, 20, 11, 5, 9, 5, 11, 20, 14, 11, 15, 5, 10, 15, 5, 16, 15, 9, 5, 10, 16, 4, 15, 11, 5, 10, 5, 26

I have been wrapping these sequences around into circles, with the first number in the sequence on top. The circle is always symmetrical across the vertical, and seems to have some other interesting properties too- summing every other number in the mod 8 circles adds up to 0 mod 8, for example. This might be a red herring though, because I can't do the same for the big mod 48 circle. I also can't explain why there are so many multiples of 5 in the mod 48 sequence.

If anyone notices any patterns in these please let me know!

>>11239109
I mistyped the third sequence. It's actually:
>7, 5, 6, 7, 5, 7, 6, 5

There was some beginner PDE an anon helped me out with in the previous thread that got deleted. I didn't actually thank that anon. Thank you fren.

>>11239109
Did u try OEIS

>>11239144
Yes. At least, I've plugged the sequences into their search and it tells me "the terms do not match anything in the table." I don't know if there's a more adept way to use it- e.g. to apply mod 8 to all their sequences and compare my first three sequences to those? Because "4" here could just as easily be -4, or 12, or something.

>>11239137
jannies are just fags sometimes. but you're welcome~

>>11239137
you're welcome~ jannies are just faggots sometimes
>>11237894
and u 2

>>11239109
Did you try interpolating those in [math]Z_8[x][/math] and checking if anything happens with the coeficients?

>>11239210
I'm too dumb to know what that means, so probably not, no. I tried fiddling around by adding multiples of 8 to each number looking for a pattern, but not in any systematic way.

>>11239223
i gather he means polynomial interpolation.
for example, i did it for the first 4 points in your first sequence (cba doing any more) and got [math] f(X)=4X^3+ X^2+2X+4 [/math] which gives [math] f(x)=3,4,7,4 [/math] for [math] x=1,2,3,4 [/math]
i guess it's worth a shot but i cant see it helping you much

>>11235344
hey sci i need some advice. I just finished up my first semester, studying aerospace engineering at college and I think I did poorly and I'm thinking about dropping out. I got a 3.5 gpa and based on my standards from high school, thats very, very bad, but I spoke with my parents about it (dad hasnt graduated high school and mom dropped out of AS degree) and they think im crazy for being disappointed in myself and wanting to drop out. I think that I should drop out, in order to not waste more time or money by failing out of the future, harder classes.
What I'm wondering is this: are these results objectively bad or good, from someone familiar with higher education, and how much harder do engineering classes get? I somewhat want to study cfd in grad school does this result harm my chances of doing that in the future?

>>11239109
>>11239125
>>11239144
>>11239210
>>11239223


Okay guys, it's me again. I think I figured it out. I think they are related to rows of this 8*8 matrix:
[1, 2, 3, 4, 5, 6, 7, 8]
[2, 6, 5, 1, 8, 4, 3, 7]
[3, 5, 1, 7, 2, 8, 4, 6]
[4, 1, 7, 6, 3, 2, 8, 5]
[5, 8, 2, 3, 6, 7, 1, 4]
[6, 4, 8, 2, 7, 1, 5, 3]
[7, 3, 4, 8, 1, 5, 6, 2]
[8, 7, 6, 5, 4, 3, 2, 1]

Obviously there's some kind of pattern here, the edges are especially obvious as they are just counting up or down. But I'd rather not right out the whole matrix for the 48*48 version. Is there some formula that concisely describes this matrix? Some property that generates its elements?

just typing up some old notes from a combinatorics course (i'm still not entirely sure what it has to do with combinatorics) and i came upon pic related. i understand the inequality arises from log being strictly increasing, but why is the inequality not strict? is it simply for the cases with [math] 0<x<3 [/math] or am i missing something else?

>>11239453
not an answer, but if i had to guess i'd say it has something do with primes based on the fact you mentioned modular arithmetic and its a latin square
something like
x 1 2 3 4 5 6 7 8
2x mod p
3x mod p
.
.
.
8x mod p

>>11239460
>simply for those cases
Yes.
>am I missing something else
Domain of definition shit, possibly, technically the equality is only in (0, 2].

>>11239492
yeah youre right. not sure why i included 2<x<3. thanks

What celestial body will humans physically visit after the Moon and Mars?

Can someone recommend a source that demystifies this crazy bullshit for a total retard (me)?

>>11239595
You can’t visit things that don’t exist anon.

I just want to thank the ME anon who helped me on my mechanics problems during the last couple of days.
God bless you, anon!

>>11238921
define "exists"

>>11239440
u sound like a fucking pussy

>>11235344
How do you solve this question? Like I took moments anti-clockwise from B but I don't seem to have gotten anywhere, I got the first two results for Bx and By, but Mb I couldn't do a think for. is i supposed to be -3(76.6) -1200 or something like that?

Guys can you help me on this excercise, I've been trying to solve it but can't.
Basically I have a sphere defined by [math]x^{2}+y^{2}+z^{2}=4[/math] and also a cilinder going through [math](x-1)^{2}+y^{2}=1[/math] and I need to get the volume outside the cilinder and inside the sphere. I tried using spherical coordinates but I'm stuck. Here is an image illustrating the problem but with different equations (notice how the cilinder is like a tube going though the sphere).

>>11240820
Well it's the two time the volume of a cylinder from 0 to sqrt(3), plus two times the volume of the cut end of a ball from sqrt(2) to 2. Find the fomula for the volume of the cut end of a ball.

>>11240820
Well it's the volume of the whole ball, minus the part that intersects with the cylinder. That intersecting part equals the two time the volume of a cylinder from 0 to sqrt(3), plus two times the volume of the cut end of a ball from sqrt(2) to 2.
Find the formula for the volume of the cut end of a ball and you're essentially done.

>>11240820
Well it's the volume of the whole ball, minus the part that intersects with the cylinder.

That intersecting part equals the volume of a cylinder from z=-sqrt(3) to z=+sqrt(3),
plus two times the volume of the cut end of a ball, one of which goes from from z=+sqrt(3) to z=+2.

Find the formula for the volume of the cut end of a ball and you're essentially done.

>>11240857
my numbers refer to the image situation, with the offset in (x,y) of the cylineder it will be more complicated, but maybe the inverted approach is still fruitful.

>>11240857
>>11240865

Many thanks

TA graded my test wrong and gave me more points. is there anything bad that can happen to me for not telling him?

>>11240457
uhh, what question?

>>11240088
might have been me. you are always welcome~

>>11240929
No, even if they retained your test papers, I guarantee that fucking no one would look through them again. TAs and professors are busy with their own research and once they finish grading your piece of shit hw and exams, they literally never think about them again.
Speaking from personal experience. Even if you went up to the TA, they would probably not give a shit enough to regrade and reenter scores, unless they were severely autistic *and* moralfaggy (requires both qualities).

>>11239767
I guarantee that you use Bayesian reasoning every fucking day of your life for almost everything you do.

>>11240972
>be me, ten years old
>go to teacher and tell her she graded me incorrectly
>just because you were honest, you'll get to keep that grade
Good old days.

>>11237077
Pussy can cure it. You can learn to like sauerkraut. Why not vaginas? Associate pleasure with it. Associate dissatisfaction with dicks.

The only tactic for explaining matrix multiplication that I know is
>explain linear maps from [math]\mathbb{R}^n[/math] to [math]\mathbb{R}^m[/math], and give examples
>explain how you can represent those as matrices, and explain matrix-vector multiplication
>explain the problem of composing two such linear maps represented by matrices, and introduce matrix multiplication as the solution
Does anyone know anything better?
>>11239767
>look through my copy of the manga guide
>it fucking skips Bayesian stats
You're fucked.
>>11241026
Anon, he's asking for a friend.

>>11239767
https://cran.r-project.org/web/packages/LaplacesDemon/vignettes/BayesianInference.pdf

It is never explicitly stated but when you use a normal distribution as a model, for instance, you're assuming measurements are some iid rv's X_i conditioned on some static mean, variance. {X_i | M=m ∩ S=s} or something similar. This is what's used for the likelihood in the typical frequentist analysis.

We may, however use Bayes theorem to treat these parameters as being random themselves. The benefits of this are: it's easier to interpret, you can incorporate known or believed information into your analysis. Like what's the probability of the probability of an event being between .4 & .6?

The downsides are: why tf should I trust your prior, the distribution attached to the random parameters (there are """""objective""""" methods for selecting these, & asymptotic results for normality). That and you get into application, often times the solutions can be exceedingly difficult to calculate or require heavy computation. The way they wrote stuff in your pic is a bit confusing, you're not that much of a dumdum desu. It's all derived from the first theorem & some corresponding math stat.

what do i call the cloud that comes out of hot drinks in cold weather, or when you exhale in cold weather?

>>11241143
those clouds are different things, I think.
>hot drink
steam, specifically saturated water vapor
>breath
probably not literal steam, more like mist (very fine particles of liquid water)

HE?

>>11241794
what about it?

>>11241798
If that's the correct answer.

>>11241085
I said explain it to a retard, not a genius.

>>11241856
Alright, alright.
Imagine you have a sack with two coins. One coin in it is cheated and falls on heads 90% of the time, while the remainder are normal.
You pick a random coin in the sack, and thow it 10 times. It falls on heads 9 times. So you stop, and you think "I've probably gotten the cheated coin."
Now, suppose the sack has a billion coins.You'll stop, and you'll think "I probably haven't gotten the cheated coin out of one billion, I was just unlucky with the throws."

Stop thinking about coins, and imagine you're a scientist. You're studying this random event.
So sometimes, you can pretend that there's a sack of random events, and that you randomly got one the one you're studying from the sack, and that the sack has some sort of distribution on it. So, say, the average distribution in the sack has average 5, or something along those lines.

Bayesian statistics is essentially that sort of thing.
Refer to anon's post for the formalism.

>>11241893
Absolutely surreal how 4chan's editor manages to completely ruin my english.

>>11241026
>Associate dissatisfaction with dicks.
The problem is, it's quite the opposite right now.

>>11239453
>>11239475

I think maybe I should actually be looking the matrix mod 9? If I do that, and convert the right half into negatives, the pattern becomes even clearer:

[ 1, 2, 3, 4, -4, -3, -2, -1]
[ 2, -3, -4, 1, -1, 4, 3, -2]
[ 3, -4, 1, -2, 2, -1, 4, -3]
[ 4, 1, -2, -3, 3, 2, -1, -4]
[-4, -1, 2, 3, -3, -2, 1, 4]
[-3, 4, -1, 2, -2, 1, -4, 3]
[-2, 3, 4, -1, 1, -4, -3, 2]
[-1, -2, -3, -4, 4, 3, 2, 1]

I still can't come up with a formula for it though.
e.g. something for the jth element of the ith row.

>>11242027
[ 1, 2, 3, 4, -4, -3, -2, -1]
[ 2, -3, -4, 1, -1, 4, 3, -2]
[ 3, -4, 1, -2, 2, -1, 4, -3]
[ 4, 1, -2, -3, 3, 2, -1, -4]
[-4, -1, 2, 3, -3, -2, 1, 4]
[-3, 4, -1, 2, -2, 1, -4, 3]
[-2, 3, 4, -1, 1, -4, -3, 2]
[-1, -2, -3, -4, 4, 3, 2, 1]

*fixed spacing

>>11242033
nvm, I think it's ignoring some of my spaces for some reason. Hopefully you guys can still see the pattern though. The square of threes in the middle surrounded by increasingly large diamonds of other numbers.

>>11241799
to what question?

>>11242039
Try using [code] tags. They work in /g/, never tried it here.

>>11242135
Doesn't work in /sci/ lad.

>>11242135
we use math and eqn tags here for latex

>>11242027
>I still can't come up with a formula for it though.
>e.g. something for the jth element of the ith row.

A formula for that matrix would be (7 - abs(j-4.5) - abs(i-4.5)) mod 4 + 1.
But that doesn't account for the negative signs.

>>11242221
Thanks, that's helpful. You could probably do it mod 8 or mod 9 instead of mod 4 to make it work out, though it might look more like this version >>11239453 than the one you responded to. It's too late in the evening for me to work out the exact formula, but if you don't come up with it I will try to generate one myself tomorrow morning, based on your input.

Explain how stds work. Why can sex between a man and wife not birth an std, but fucking strangers does birth stds? Is it an immunity thing like you and your partner have a certain strain of std causing bacteria, but because only you two are touching each other your body fights the bacteria so it doesn't create an std?

>>11238498
Welche Uni?

>>11242456
what the fuck are you ratrded

>>11242799
Why can't you answer?

>>11242810
he’s intimidated, finish him

>>11242799
All that is given online about stds is that bacteria that creates stds are found in semen, blond, etc.. So metaphorically speaking we are suffering from the same mechanism that works in The Walking Dead. On a technical level every human being is on the road to being infected with an std. We all carry std causing bacteria. Why does the bacteria "evolve" humans into std creatures with outside the confines of marriage sex?

>>11242862
>blond
FUCK YOU AUTOCORRECT AND FUCK THE HORSE YOU RODE IN ON

>>11242862
That guy is stupid. He can't answer.

Is there any better programm for finding analytic solutions to odes than mathematica?

>>11242877
based and aggressively retardedpilled

also checked

>>11242927
I wouldn't think so, but it may well depend on the kind of ODE

Are people in this thread >>11241631 pretending not to get the filtered algebra joke or actually serious?
I really can't make the distinction.

>>11241084
>Does anyone know anything better?
there is nothing better

https://www.reddit.com/r/AskPhysics/comments/edhrok/intro_quantum_mechanics_group_study_for_spring/
Anyone interested?
I'm range banned from starting a new post so can some Anon start a new thread for me? Thanks

Given two power series, how do I prove that one is greater than the other?

>>11242927
Matlab (it's free from my college)

>>11243205
You don't, usually.
In specific problems some proofs from monotonicity of the difference or pointwise comparisons might show up, but there's no general method.

why can't thunder go in straight line?

>>11243489
Because the surfaces of equipotential up in the clouds are all crazy and curvy and bumpy in a random way. I'm sure there's a better explanation. This is an interesting question.

>>11243489
It could if it had a straight path. The heat creates an obstacle for itself, too. Vaporizing its path.
>>11243504
That sounds good too.

>>11243489
Wind.

How do I cite values I got from a website in a table or a graph on my lab report? What about the results of measurements I performed?

How do I cite my tables/graphs? Put the [1] next to every value? In the caption for all? What about my own measurements, do I need to do anything?

>>11243614
Typesetting standards aren't universal, lad.
Throw names of your professors on arxiv or sci-hub until you figure out how do they cite tables.

So why do you have to attach alligator clips to the terminals of batteries? Couldn't you wrap copper wire around them like you would the screw terminals in a light switch?

>>11243669
Sure. Maybe some tape.

>>11243680
But why exactly do you need alligator clips? Is it simply for convenience?

>>11243685
Yeah. You don't NEED them. They are fast and grip well.

>>11243669
The wire would be electric once attached and difficult to remove again when not needed anymore, you would need gloves at least.
The clips are the right tools for the job.

>>11243703
>>11243669
Dude. Don't be a puss. You just grab 'em. It doesn't hurt. You can twist wire into a tapered coil and kinda screw on.

>>11242221
>>11242272
Ok, figuring out a formula for the signs is harder than I thought it would be. Here's a simpler question that will help me work my way up to it:

What is the formula for the A_ij in the following matrix?

A = [
[1, 1],
[1, -1]
]

>>11243731
If we're using 0-based indexing it's 1-2ij.

>>11243810
Hmm, ok. And then what about this matrix?

B = [
[1, 1, 1, 1],
[1, 1, 1, 1],
[1, 1, -1, -1],
[1, 1, -1, -1]
]

Does anyone have some recommendations for analog telescopes in the $500-$1000 range? I want to see the Galilean moons in decent resolution.

>>11243818
ehh [math] 1-2 \lfloor \frac{i}{2} \rfloor \lfloor \frac{j}{2} \rfloor [/math] I guess, if you don't mind the floor function

>>11243848
Ok. I'm still having trouble figuring it out... one more, if you don't mind.

C = [
[1, 1, 1, 1],
[1, -1, -1, 1],
[1, -1, 1, -1],
[1, 1, -1, -1]
]

>>11243910
Just repeat the same trick anon used earlier.

>>11244168
I'm sorry, I still can't figure it out. It's different from the others because there's a line of positive ones going through the negatives.

>>11244203
Oh, right, didn't notice.

If two subsequences converge to two different values, then the sequence does not converge.

Can someone please write a proof for that using just the definitions of a sequence and subsequence? I'm guessing proof by contradiction would be the easiest way?

>>11244347
>proof by contradiction
Yeah. Show any subsequence of a given sequence has the same limit as the original sequence, and couple that with the uniqueness of the limit.

>>11244347
show that if a sequence converges, then all subsequences converge to the same value [hint: use triangle inequality]

alternatively by contradiction:

suppose two subsequences converge to two different values, and further that the sequence converges. pick epsilon to be half of the smallest distance between the three convergence values. then the contradiction arises when you find that there are infinitely many values attained by the sequence that are bigger than epsilon

>be me
>make a pun thread
>start out by joking that I was filtered in my maths grad program, and now have to study filtered algebras
>people reply seriously
>not a single pun back
>janny deletes it
>might actually get a three day ban later for off topic
Why do I even still post here?
Does anyone have a good reason to post in /sci/, outside of this thread and /mg/?
>>11243031
Thanks for the reply.

>>11244489
A three day ban? It's time you popped your cherry.

You still post here because it's fun to help people and talk about /sci/ence. Also you like me. There is no good reason to post on /sci/, but you won't leave.

Not the other anon, but yeah there's nothing more intuitive than explaining how a transformation matrix acts on a vector.

>>11244514
>popped your cherry
I've already accumulated ~5 months of ban time, lad.
>you like me
See you soon, honey.

>>11244534
>only 5 months
lol

>>11235344
why the fuck does t = s0/2k ?

>>11244630
[eqn]\frac{ds}{dt} = -2k \Rightarrow ds = -2kdt \Rightarrow \int_{s_0}^0 ds = \int_{0}^{t} -2kdt \Rightarrow 0 - s_0 = -2k(t - 0) \Rightarrow s_0 = 2kt \Rightarrow t = \frac{s_0}{2k} [/eqn]

>>11244730
the section I'm in hasn't gone over integrals yet, so there's a way to solve it without integrals

>>11244809
>solving seperable differential equations without talking about integration
your book sucks then.
You know why [math] \dot{s}=-2k [/math] , right? That means that the rate of change of side length is constant, and side length runs from [math] s_0 [/math] to [math] 0 [/math]. So [math] \Delta s=-s_0 [/math]. But "time" is equal to (change)/(rate) so [math] t=\frac{-\Delta s}{-\dot{s}}=\frac{s_0}{2k} [/math]
Basically, just use definite integrals. This is the most direct way to understand this without hand-waving.

>>11244809
>solving seperable differential equations without talking about integration
your book sucks then.
You know why [math] \dot{s}=-2k [/math] , right? That means that the rate of change of side length is constant, and side length runs from [math] s_0 [/math] to [math] 0 [/math]. So [math] \Delta s=-s_0 [/math]. But "time" is equal to (change)/(rate) so [eqn] t=\frac{\Delta s}{\dot{s}}=\frac{s_0}{2k} [/eqn]
Basically, just use definite integrals. This is the most direct way to understand this without hand-waving.

>>11244850
yeah it makes sense, I was just trying to see if there was a way to solve it in the context of what was already covered in the chapter. thanks for the help

>>11244871
what book is this~?

>>11244878
Thomas' Calculus

subtitled: Including Second-Order Differential Equations

Just started learning about orbital mechanics from the books in sticky.
Do you know of any good tools/websites to visualize orbits and related things?
Thanks

How many hours do you sleep, /sci/? And when do you sleep?

>>11245564
Grab your balls and make a thread. 12:00-3:30 or 4:00. Catch an hour or two nap every other day. Good enough.

>>11235344
I need help with this:

The problem is to find the maximum- and minimum area created by the area of the triangle ABC where [math]k>1[/math], see pic related the light-blue area. Point A is the intersection point of equation
[math]f(x)=k\cdot k^{x}[/math]
and
[math]g(x)k\cdot(\frac{1}{k}^{x})[/math]. Point B and C are created by the tangent lines of their respective equation as they are intersecting the x axies.

Also, merry christmas

>>11245564
4-6 hours. 1-3 am to 5-9 am

>>11244534
ive got 5+ months just in ban evasion bans

>>11245535
kerbal space program

>>11245564
theres a sleep thread already up, has a coffee pepe

>>11245598
he knows that retard

>>11245606
how do you know he's a he?

>>11245564
not enough

>>11245583
I will take a crack at it when I get home. Doesn't look easy. Merry Christmas~!

>>11235344
Is there a nice for formula for the element in the ith row of the jth column of this matrix?
[
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 0, 0, 1, 1, 0],
[0, 1, 0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 0, 0, 0, 0, 1, 0],
[0, 1, 1, 0, 0, 1, 1, 0],
[0, 0, 0, 0, 0, 0, 0, 0]
]

>>11245649
Ah, missed a row, my bad!
correct version below:
[
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 0, 0, 1, 1, 0],
[0, 1, 0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 0, 0, 0, 0, 1, 0],
[0, 1, 1, 0, 0, 1, 1, 0],
[0, 0, 0, 0, 0, 0, 0, 0]
]

>>11245583
[math]B=( - \frac{1}{\log k}, 0)[/math], and since f(x)=g(-x), [math]C=(\frac{1}{\log k}, 0)[/math].
Since [math]A=(0, k)[/math], the area is [math]\frac{k}{\log k}[/math].
This goes to infinity when k goes to either one (since log 1=0) or infinity (since k grows faster than log k).
Calculating the derivative and equalling to zero, you get log k=1, and k=e.

Merry Christmas.
>>11245564
7-10 hours.
Weekdays it's around midnight until 7.

>>11234121
Techmuller space is the space of differential structures on a Riemann surface modulo conformal transformations. "Inter-universal" is just a buzzword for describing how the analytic geometry is related to arithmetic geometry.
>>11236487
On a topological vector space [math]V[/math], the determinant on [math]TV[/math] determines the determinant line bundle of [math]V[/math]. The determinant line bundle then determines the orientability of [math]V[/math] in the sense that all principal [math]O(d)[/math]-bundles must factor through the determinant line bundle.
>>11236881
That's due to Kirchoff's loop rules, which is part of graph theory.
>>11238456
First we notice that [math]\ln[/math] maps [math]\mathbb{C}\setminus\{0\} \cong\mathbb{C}^* \rightarrow S^1 \times (0,\infty)= C_\infty[/math] to the semiinfinite cylinder on the principal branch, hence we see that [math]f: \mathbb{C}^*\rightarrow \mathbb{C}^*[/math] defined by [math]f(z) = z^z[/math] pulls back to [math]\ln f : C_\infty\rightarrow C_\infty [/math] as [math]\ln f(z) = z \ln z = z(\ln r + i\theta)[/math]. Hence holomorphicity of [math]f[/math] on [math]\mathbb{C}^*[/math] is equivalent to holomorphicity of [math]\ln f[/math] on [math]C_\infty[/math]. We can then develop the Laurent series for [math]z\ln z[/math] on [math]C_\infty[/math] then push it forward back down to [math]\mathbb{C}^*[/math] to obtain a Laurent series for [math]z^z[/math].
>>11241084
>Does anyone know anything better?
Look at linear representations of the semisimple multi-fusion category [math]\mathcal{M}_{n\times n}(\mathbb{R})[/math] of [math]n\times n[/math] matrices (hint: look at how the identity decomposes on the units).

>>11245613
You can tell by the way they type it it is more than a few words. I have never been wrong with, "woman detected."

>>11236487
it measures either the change in (signed) volume before and after a transformation, or it measures (signed) volumes themselves. even shorter answer is: it just has to do with volumes. but often they don't tell you any of this. they just give you an ugly formula together with one application (matrix is invertible iff determinant is non-zero) without any geometric insight.

>>11236795
a lot of stuff in mathematics eventually "boils down to something". does this mean that "stuff" is the same as "something" ?
I mean almost everything in linear algebra "eventually boils down" to solving systems of linear equations. but it would be foolish to think that you can learn systems of linear equations and be done with linear algebra.

>>11236487
determinants are just a distraction from developing linear algebra from the theory of Noetherian k[x] modules

>>11245791
>amps up the illegibility up to the sky specifically when replying to me
Ugh.
I've figured out what's a multi-fusion category, but can you point me to the construction of the category of n x n matrices?
Specifically, are the objects in it [math]R^n[/math], n a natural number, or am I completely beyond lost?

>>11245932
The objects are matrices themselves, with the semisimples being elements of the the natural basis [math]E_i[/math]. It's a special spherical 2-groupoid and the simplest realization of a SMFC.

>>11245943
>objects are matrices themselves
Should've expected that.
What are the morphisms, conjugation?

>>11245959
Write a matrix [math]M \in \mathcal{M}_{n\times n}(R)[/math] as [math]M = \bigoplus_{ij} m_{ij} E_{ij}[/math], where [math]R[/math] is a [math]\mathbb{Z}_{\geq 0}[/math]-module and [math]m_{ij}\in \mathbb{Z}_{\geq 0}[/math], with [math]E_{ij}[/math] the indicator matrix of the [math](i,j)[/math]-th sector. A morphism [math]f = (f_{ij})[/math] maps [math]f_{ij}: m_{ij}E_{ij} \rightarrow k_{ij}E_{ij}[/math] and is hence a module homomorphism [math]R^{m_{ij}} \rightarrow R^{k_{ij}}[/math].

>>11235410
knockout elephants

The number of ways of arranging n students in a row such that no two boys sit together and no two girls sit together is m(m>100).

If one more student is added, then number of ways of arranging as above increases by 200%, The value of n is:

WAT DO

>>11245791
>That's due to Kirchoff's loop rules, which is part of graph theory
How does graph theory relate to group theory? Specifically, what are the elements of the set the RC circuit group acts on? What's the operator?
Explain like I'm mentally incapacitated pls.

>>11245986
Got it, thanks.

is it scientifically possible to go back in time?

>>11246012
no

>>11246003
Naively speaking group theory would definitely be relevant in studying graph isomorphisms; e.g. vertex/edge permutations. I'm not an expert in combinatorics though so I'm not aware of any deeper relationships.

>>11245997
Something something depends on whether n is even or not, because it needs to go boy girl boy girl etc, something something if it's even you can put all the boys in either the even seats or the uneven seats, otherwise you're stuck putting the larger group in the uneven seats, something something just consider the possible ways of ordering the boys and the girls by themselves in either unever or even seats.

>>11246015
Th-thanks babe

I think the concept of potential energy is retarded, please explain to me why I'm retarded

>>11246118
>a question I think I can answer
Gravitational potential energy is still energy. Think of it like the force already exerting on an object overcoming the opposing forces stoppping it from falling, or those forces disappearing e.g. when letting go of a ball.
t. fellow /sci/let

is there a name/term for the sinusoidal wave made from the union of a bunch of semicircles?

>>11246118
See
>>11238925

>>11245724
Thank you!

>>11246118
>I think the concept of potential energy is retarded
What do you mean retarded?
Do you not understand it? Do you not see how it is applicable to solving problems? Do you not understand the empirical or mathematical basis for energy? Does the meaning behind conservation of energy escape you? Do you not understand why a force vector field can usually be assumed to have a potential?
Be specific.

>>11238921
>>11246118
"Energy" is represented by [math]H\in C^\infty(M)[/math] on a symplectic manifold [math](M,\omega)[/math], called a Hamiltonian function. The Hamiltonian vector field [math]X_H[/math] satisfies [math]dH + \iota_{X_H}\omega = 0[/math], and it always exists and is unique. In quantum mechanics, the energy is represented by the a local Hermitian operator [math]H[/math] called the Hamiltonian, which generates the ESA operator of time evolution [math]U(t) = \exp\left(-i Ht\right)[/math] with a dense domain of definition.
In either case, the kinetic energy [math]K[/math] is defined as the "maximal" term in [math]H[/math] that is bilinear; namely [math]K = Q_q(q,q) + Q_p(p,p)[/math] for some ([math]c[/math]-number or operator) quadratic forms [math]Q_{q,p}[/math], invariant under symmetries of [math]H[/math], and such that the potential energy [math]H - K[/math] cannot be written in terms of a single dependence on [math]Q_{q,p}[/math]. By this definition, the potential energy always exists.

>>11246014
why?

>>11246490
because it violates causality and there is no evidence it is possible

>>11246534
> it violates causality
why?

why are books so boring?

>>11246547
Why is life so boring?

>>11246547
You are either better than or not as good as the rest of humanity. I don't know you so, you decide.

>>11246546
Because traveling backward in time implies a negative spacetime interval between your starting positing and target position which implies a spacelike world line. Events separated by a spacelike interval are not causally related. But if you travel back in time from the location of your bedroom to your bedroom 1 hour ago, clearly you are in a position to affect the environment of your bedroom. This is a contradiction.

>>11246547
You need better books.
Try A Certain Magical Index, Racine's Phaedra, René Girard's "Things Hidden Since the Foundation of the World" and Villani's Birth of a Theorem.
You should enjoy at least one of these.
>>11246563
Life is fun.

>>11246546
Because traveling backward in time implies a negative spacetime interval between your starting positing and target position which implies a spacelike world line. Events separated by a spacelike interval are not causally related by definition. But if you travel back in time from the location of your bedroom to your bedroom 1 hour ago, clearly you are in a position to affect the environment of your bedroom. This is a contradiction.

>>11240820
where did you get this exercise?

>>11246534
but if you got back in time and killed your grandpa then you won't die because you are from a different dimension

>>11246623
That's not time travel, that's inter-dimensional travel.

>>11246645
yes

>>11245649
>>11245650
The only way I can think of to do this is with kronecker deltas at each 1. Which technically works, but doesn't seem particularly elegant. I would think that there would be a simpler way, leveraging the symmetry apparent in the matrix.

retard here, I heard that having a beard can slow the aging process so can having a small beard give me the same effect?

>>11239109
>>11239453
>>11242027
>>11242221

I bit the bullet and made a program that could generate the 48 by 48 matrix. Does anybody have any idea what this is? There's clearly a pattern here. It's especially evident looking at the center and the perimeter. But it's hard to tell what's going on in the in between areas.

>>11235344
why are things taboo?

This should be elementary, yet I'm coming up short of ideas as I never had to do this exact thing: how do I remove, substitute, rearrange or at least cleave a side of that single nitrogen atom without breaking up the rest of the molecule? Rearrangements are fine, but breaking the structure isn't.

if we r in a simulation can we get over it or at least try to control the owner?

Why were ancient people so stupid when it comes to the believing in afterlife despite they were good at math and logic?

My uni course says that homework will be graded or sent back for revisions in a week after submitting, but it took them 3 weeks and now I have to spend time during christmas to make modifications, is there anything I can do to make life hell for these people?

is it better to sleep 12h than 8h for my brain long term?
pls say yes

>>11247743
Are we talking about eight hours of good sleep or eight hours of absolutely garbage sleep, starting with two hours of random thoughts, broken up a couple of times by waking up from weird dreams and going to the bathroom, and finishing up because of this godforsaken light that goes through the exact gap in your blinds to hit you in the eyes?

>>11247750
wat?

>>11247859
Are we talking about eight hours of good sleep or eight hours of absolutely garbage sleep, starting with two hours of random thoughts, broken up a couple of times by waking up from weird dreams and going to the bathroom, and finishing up because of this godforsaken light that goes through the exact gap in your blinds to hit you in the eyes?

>>11247859
Do you sleep well?

>>11247912
y

>>11247750
please go back or lurk long enough to be able to spot shitposting

Can someone link me to some versions of the central limit theorem that is formulated just with functions and integrals rather than stochastic notation?

>>11243810
What methods would I use for finding a formula like this? Do all matrices have such a formula?

>>11247730
Because math and logic has literally nothing to do with finding out what happens in the afterlife. Math and logic doesn't automatically mean you are suddenly an omniscient being either, or even a particularly smart individual for that matter. You can't expect that to be enough of a reason to know everything. For all we know we could also be as far away from the truth as they were, but we just think their ideas are ridiculous now because of our modern beliefs.

If I were to pick a wave with set frequency and amplitude, and overlap it with itself a thousand times, with different, random phase times, what would the final wave look like?

can anyone make sense of this?
[math]dp_0 dp_1 dp_2 dp_3\ \delta(p_0-E)=dp_1dp_2dp_3[/math]
[math]\vec{p}[/math] is a four-momentum and [math]\delta[/math] is the dirac function

>>11248235
?

>>11248235
A straight, horizontal line

>>11248235
?

>>11248345
The equality is after integration [math]\int_M d^4p \delta(p_0 - E) = \int_{\Sigma_E} d^3p[/math], where [math]\Sigma_E = \{p\mid p_0 = E\}\subset M[/math] is a constant-energy surface.

>>11247966
Then what do you need twelve hours of sleep for?
>>11247990
Are you sure?
>>11248045
Polynomial interpolation on two variables.
Also wild guessing.
>>11248235
>random phase times
The expected value for the random phases disappears and you're left with the original function.
In practice it looks squiggly.
>>11248433
Random phase times, anon.

>>11248446
>not saying it's an equality in the sense of distribution theory
Who are you and why are you attaching Yukari to your posts?

>>11248456
you are extremely autistic

>>11248470
At least I'm not a doo doo head.

>>11248462
>in the sense of distribution theory
Well in the sense of currents actually.

>>11246744
Stop believing bullshit. No.
>>11247445
We live in a society.
>>11245535
GMAT
>>11248462
>he doesnt know
>>11248470
Dont insult my boyfriend

>>11248456
>Random phase times, anon.
What do you mean?

>>11248494
Also works.
>>11248510
I didn't read the formula.
This does bring me to the question, tho:
how the fuck does it get that close to 1000?
Can you run it again, only summing four or five?
Maybe it just randomly selected a single real number, instead of one for every element of the sum?

Given two functions, f : R to R+ and g(x) = e^(-f(x)), how do I prove that g is limited? I'm thinking of finding the limit as x approaches infinity, but I'm not sure that's enough.

>>11248516
Sure.

>>11248528
By limited do you mean bounded? If you can show that e^-x is bounded on R+, you're set.

>>11248535
Huh, weird.
Thanks.

>>11248535
One more thing, my bad.
Can you set that random real interval to [0, 2pi]?

>>11248565
No problem, I am curious too.

The amplitude gets cut down by a lot.

>>11248572
>cuts down all the way to twenty
Nice, but I expected lower tbqh, see pic related.
It seems the original intuition was right and it should go down to zero, but either wolfram's random generator is pretty skewed or 1000 is just way too small.

>>11248582
>Nice, but I expected lower tbqh, see pic related.
I tested a few times, and I got values from 5 to close to 50 with 1000.

So I tested with 1e6...

>>11248601
>it fucking goes up
Huh, the variance really drags it around.
Thanks again.

>>11247704
Atoms don't have "sides"

never been to /sci/ before. are stupid medical questions allowed?

>>11248456
Thank you. I don't know too much about interpolation. When I go on wikipedia's page for multivariable interpolation here: https://en.wikipedia.org/wiki/Multivariate_interpolation
they list a number of methods. Since I'd rather not go down any pointless rabbit holes, do you know which method(s) would be most fruitful for a matrix like the one pictured in this comment: >>11246837
?

>>11248713
yes, use the /med/ general for those.

>>11248754
cheers

Why is the inverse slope reciprocal and negative? I get the negative part, why reciprocal though? I understand that it works, I just don't get it how does it work so smoothly lol

My hair is more puffy on one side of my head than on the other. Is it true that this may be because I'm always sleeping with one side of my head on a pillow?

>>11248742
Bilinear.

>>11248761
Two segments are perpendicular only if the inner product between two unit vectors along those segments is zero. The inner (or dot) product between these vectors is defined as (rise in seg 1)(rise in seg 2)+(run in seg 1)(run in seg 2)=0. You know the rise and run in 1, solve for slope 2 and you get that it is the neg reciprocal of slope 1.

>>11248661
I guess I can confirm it wasn't mathematica's generator or at least it wasn't it alone.

With 1e7, the amplitude varies to more than a 1000 often.

Is the exterior algebra a quotient of a polynomial ring? If [math]V[/math] is an [math]n[/math]-dimensional vector space over a field [math]F[/math], can I express [math]\bigwedge V[/math] as [math]\left.F[x_1,\dotsc,x_n]\,\middle/\,I \right.[/math] for some ideal [math]I[/math]?

>>11248877
The exterior algebra is anticommutative, anon.

>>11248884
shit forgot about that
sorry for being retarded

>>11248891
No biggie.

>>11246462
Yukariposter, how do I get to your level?
>inb4 faggot
Seriously, the responses Yukariposter comes up with are a goldmine for someone wanting to study mathematical physics like myself.

>>11248802
Why is this?

>>11248917
That's basic mechanics, tho.

>>11248785
By that method every four points will have a different equation though.

https://en.wikipedia.org/wiki/Bilinear_interpolation
>It is assumed that we know the value of f at the four points Q11 = (x1, y1), Q12 = (x1, y2), Q21 = (x2, y1), and Q22 = (x2, y2).

For example, practicing on the four points in the center of this matrix:
[ 1, 2, 3, 4, -4, -3, -2, -1]
[ 2, -3, -4, 1, -1, 4, 3, -2]
[ 3, -4, 1, -2, 2, -1, 4, -3]
[ 4, 1, -2, 3, -3, 2, -1, -4]
[-4, -1, 2, -3, 3, -2, 1, 4]
[-3, 4, -1, 2, -2, 1, -4, 3]
[-2, 3, 4, -1, 1, -4, -3, 2]
[-1, -2, -3, -4, 4, 3, 2, 1]

I got the formula:
f(x,y) = 243 -54x -54y +12xy

This works for those four points, but when I plugged in x = 1, y = 1, I got f(1, 1) = 147, when it's supposed to be 1.

I have a question that has been keeping me up at night about my career.

I'm planning to get a PhD in physics and continue in research, I've got my BSc degree in pure physics and currently I'm doing my MSc of research in nanomaterials in the same university, I was accepted in prestigious Universities in the country but decided to stay in the same one even though I hate this MSc because one of my professors told me that he will GUARANTEE me doing great project with me, especially that he has some good contacts and his level is incredible.

The problem is that the education is fucking shit, some professors aren't serious, it happens often that I correct two professors who are dumb cunts.

This University is ranked 49th/100 universities in the country, will graduating from it affect my CV?
It would be fucked up since I was accepted in top 10 universities in the country and didn't take them.

>>11249267
You aren't supposed to use bilinear to interpolate more than four points desu.
You'll need to construct higher analogues by hand.
>how do I construct higher analogues
Look at the "Alternativa Algorithm" in the bilinear interpolation page, and let it deeply inspire you.
Think "man, how would I copy this with a larger polynomial in two variables."

>>11249307
Nevermind, I found it on the internet after searching for a few minutes.
https://ece.uwaterloo.ca/~dwharder/NumericalAnalysis/05Interpolation/multi/

Weird how wikipedia doesn't really mention it.

>>11249300
Can't speak in general terms, but from what I've seen, experience and know from colleagues .. it weighs way more with whom you do your final thesis with, what the quality of your work is etc. Get a paper in a nice journal out of it, if possible, attend a conference and whatnot. I doubt anyone will care about where you did your undergrad.

At least to some degree. If you come out with a completely shitty physics background, then even a great thesis and great supervisor might not fully save you. I doubt that's the case though. If your prof has good contacts, that might be worth it alone - you can get in touch with those people about PhDs, yadda yadda.

The USA was the only place I've been to where the uni ranking mattered for undergrad. Maybe the UK to a smaller extent.

>>11248917
Read Simon & Reed's texts on methods of mathematical physics back to back.

>>11249307
>You aren't supposed to use bilinear to interpolate more than four points desu
But I asked you about a method for the matrix depicted in this comment >>11246837, which obviously has way more than four points desu

>https://ece.uwaterloo.ca/~dwharder/NumericalAnalysis/05Interpolation/multi/
okay, I'll check that out.

>>11249322
>it weighs way more with whom you do your final thesis with
The guy is well known nationally, he noticed my high level and that's why he wanted me to stay with him

Even though the education level is really shitty, I study with him once a week and also in private some physics domains that we don't study

thank you so much for the advice

0 = 0a for any a, therefore 0 divides 0.
>We proceed on the understanding that 0 does not divide 0
Then why the FUCK does your definition of divisibility allow for it?

>>11249381
>0 = 0a for any a, therefore 0 divides 0.
?

>>11235344
I understand why the given answer works, but I don't understand why you can't substitute (u^2 +2u)^1/3 in for t and then take the derivative of s. Also, how do you make the math look better like in
>>11238322

there should be a sticky in SQT showing how to do that

>>11249492
>but I don't understand why you can't substitute (u^2 +2u)^1/3 in for t and then take the derivative of s
You can.

>Also, how do you make the math look better like in
With math and eqn tags.

>>11249530
>You can.
shit I tried it twice before and it didn't work, and now it does.
>With math and eqn tags.
is there a guide somewhere?

[math]f(x) =x[math]

>>11249552
That, but with a /math instead of math in the second bracket.

>is there a guide somewhere?
Yeah, on the /sci/guide linked in the sticky.
https://sites.google.com/site/scienceandmathguide/other/-sci-infographics/joseflatex.png?attredirects=0

>>11249565

thanks

>>11249565
>>11249579
Also, it's a bit outdated, in that /sci/ now does support matrices.

>>11249472
According to a common definition of divisibility, a divides b if b = ax for some integer x. Clearly, 0 = 0x for any x, so 0 divides 0

>>11249609
>According to a common definition of divisibility, a divides b if b = ax for some integer x.
only if a!=0. 0 divides no number by definition.

>>11249609
x must be unique, otherwise we can show that x_1 = x_2 which is clearly a contradiction. Since x cannot be unique for 0, we must exclude 0 from this definition of divisibility in order for it to be valid.

>>11249062
I don't really know enough about statistics to explain why.

Could be some effect of a pseudo random generator, in my shitty C code, the random seed for each thread of my CPU is probably much less random than matlab's or mathematica's, and I get a higher amplitude across all n.

How do we determine an object's velocity after a force has been applied? Assuming it was either at rest or in constant velocity before hand, and in an inertial reference frame.
Is it simply the vector sum of its original velocity (before the force was applied) + acceleration * time (how long the force was applied)?

>>11249805
>Is it simply the vector sum of its original velocity (before the force was applied) + acceleration * time (how long the force was applied)?
Not quite. This is only true for constant net force/acceleration. Use the impulse-momentum theorem.
[eqn] \Delta\mathbf{v}=\int_{t_1}^{t_2}\frac{\mathbf{F}_{net}}{m}\text{ d}t [/eqn]
Or you can use energy methods like the work-energy theorem, or variational methods. Mechanics can be as complicated as you want.

>>11249852
That actually makes sense to me, although I have never heard of the theorem.
>Mechanics can be as complicated as you want
I'm very meticulous and tend to make things overly complicated because I want to understand it inside and out before moving on. Do you have a text you would recommend for someone who has had a fair amount of mathematics but has never actually taken a physics course?
Also, just to be clear, we actually get our final velocity (the objects velocity after the force(s)) by adding the initial velocity to the RHS of the equation? And tto find its position we simply integrate over velocity from t1 to t2 (plus initial position) ?

>>11249696
I may be wrong here but if the random phase differences are uniformly distributed in [0,2pi] then the expected value of our sum of N randomly phase shifted sine waves is 0 and the variance is N/2pi.

So we can expect the amplitude to increase linearly with N.

>>11249974
>So we can expect the amplitude to increase linearly with N.

I misspoke here. This statement is inaccurate.

Certainly we can bound the amplitude of the sum by N. I wonder what we can say about the amplitude growth given the statistics found earlier and this bound.

>>11248503
Sorry, Google isn't helping. Is GMAT some tool?

>>11248446
but my notes just say [math]d^4p\ \delta(p_0-E)=d^3p[/math] and then substitute it in other equations where there isn't any integral, how do i make sense of that?
i hate this lack of rigor in my notes

>>11249899
>theorem
It's called a theorem, but it really just follows from the definition of impulse, momentum, and Newton's second law. It can be "proven" in like 2-3 lines lol
>text
If you already have training in math and don't want to slog thru the absolute basics, read Classical Mechanics by Taylor.
>just to be clear
The LHS is the change in velocity. Add the LHS to whatever the known initial v was to get final v.
>integrate over velocity
No.
>>11250159
Yes. Open source tool from NASA for mission analysis. It's probably overkill for what you want.

>>11250228
>GMAT
thanks will check it out

Is this fake?
https://youtu.be/ceR4a-81Wdg

>>11250258
No.