/sqt/ - Stupid Question Thread: Sheaves Edition

File: sheev3.jpg (18KB, 400x400px) Image search: [Google]

18KB, 400x400px

I think I got it, so [math] \varphi(U)(s)|_V=0 [/math] implies [math] \varphi(V)(s|_V)=0 [/math] by the sheaf morphism condition, so [math] s|_V\in \ker\varphi(V) [/math] which gives [math] (U,s)=(V, s|_V)\in (\ker\varphi)_p [/math].

>>8591198
Isn't that just a trivial result of the fact sheafification induces an isomorphism of stalks?

File: a75.png (304KB, 406x406px) Image search: [Google]

304KB, 406x406px

>>8591250
You're probably right but I don't know how to see it

>>8591260
Is the sheaf kernel defined as the sheafification of the presheaf kernel in what you are reading?

File: Capture.png (46KB, 642x170px) Image search: [Google]

46KB, 642x170px

>>8591275
Hartshorne says the presheaf kernel is already a sheaf, no sheafification required

File: 20170108_222817.jpg (2MB, 1739x1284px) Image search: [Google]

2MB, 1739x1284px

Please h-h-help guys
1/6 question

File: 20170108_222451.jpg (3MB, 2120x2344px) Image search: [Google]

3MB, 2120x2344px

2/6 a

File: 20170108_223004.jpg (3MB, 2120x2397px) Image search: [Google]

3MB, 2120x2397px

3/6 Part a 2

File: 20170108_223022.jpg (3MB, 2120x2020px) Image search: [Google]

3MB, 2120x2020px

4/6 Part b

File: 20170108_223051.jpg (3MB, 2120x2689px) Image search: [Google]

3MB, 2120x2689px

5/6 Part c

File: 20170108_225301.jpg (4MB, 2120x2835px) Image search: [Google]

4MB, 2120x2835px

6/6 Part D
T-t-thanks guys.

I have 20 chickens
Every 10 minutes, every chicken lays an egg, 1/10th of the eggs become chickens after 10 minutes (the rest don't develop into chickens)
1. How many chickens do i have after 8 hours?
2. What's the equation for this? I'm assuming something is integrated and it seems really simple but i guess i'm too tired to understand it.

File: ss-000058.png (46KB, 839x589px) Image search: [Google]

46KB, 839x589px

Explain this to me as I don't understand it.

How is the probability that there are two of the same die be 90/216? I understand how that value is produced by subtraction of the probability that all the dies are different and that all the dies are the same however I don't understand the reasoning for

>(If you want to convince yourself of this, think of it this way: There are six possible values that A could be, five possible values of what B could be, and three possible choices of which die could be B. This is 6 x 5 x 3 = 90 combinations out of the 216).

Shouldn't it be 6 possibilities for the first die, 5 possibilities for the second and two possibilities (either the same as the first or the second die) for the last, ergo, 6*5*2 = 60 and the probability for exactly two being the same be 60/216?

>>8591580
>Shouldn't it be 6 possibilities for the first die, 5 possibilities for the second and two possibilities (either the same as the first or the second die) for the last, ergo, 6*5*2 = 60 and the probability for exactly two being the same be 60/216?
youre not counting the 30 cases where the first two dice are the same

>>8591582
That possibility is excluded because the second die cannot have the same value as the first. The third die is the one that makes the pair.

>>8591589
>That possibility is excluded because the second die cannot have the same value as the first.
why not?

>>8591590
Six probabilities for the first die (any number from 1-6). Second die is constrained to 5 values (1-6 exempting the value of the first die).

>>8591595
>Second die is constrained to 5 values (1-6 exempting the value of the first die).
why? youre just not counting these valid cases of 2 matching dice for some reason
(1,1,2) is a 2 match just like (1,2,1) or (2,1,1)

there are 6 3-matches (A,A,A)

you can change any of these 3 to one of the 5 values of B =! A to get a 2-match

so 3*5=15 'switches' of a 3-match give a 2-match

and there's 6 3-matches, so 6*15=90 2-matches

>>8591603
Got it.

It took me 4 posts to get the Sheeve joke

File: IMG_1816.jpg (1MB, 4032x3024px) Image search: [Google]

1MB, 4032x3024px

>>8591357

File: image.jpg (2MB, 4032x3024px) Image search: [Google]

2MB, 4032x3024px

>>8591396

anyone know of some decent videos/online notes for babby model theory?

File: Untitled.png (68KB, 642x438px) Image search: [Google]

68KB, 642x438px

What is the meaning of that goofy looking O?

>>8591681
So am I all good? Sorry I can't read some of the writing properly. Thanks for helping out!!!

>>8592211
iirc its order

so in your pic, it means terms of order at least dx^2

i.e. Adx^2 + Bdx^3 + Cdx^4 + ..... for some A,B,C...

How can I scientifically last longer in bed? Yesterday I came just from my girlfriend rubbing on me and then I pretended not to want to have sex to hide the fact that it happened. We're supposed to have sex today instead and if I don't cum at insertion I'll do so in like 10-30 seconds. What do I do?

>>8592224
tactical wank m8

>>8592231
care to explain?

>>8592223
Thanks that would make sense in the context

>>8592211
What >>8592223 said is partially correct, but it's not the full story. In general, [math]f(x) = \mathcal{O}(g(x)) \text{ as } x \rightarrow \infty \Leftrightarrow \exists M > 0 : \exists x_0 \in \mathbb{R} : \forall x \ge x_0 : |f(x)| \le M|g(x)|.[/math] Basically, at some point [math]x_0[/math] the ratio [math]\left|\frac{f(x)}{g(x)}\right|[/math] can be approximated by the positive real number [math]M[/math] once we pass the point [math]x_0.[/math] If we're only interested in this around a point [math]a,[/math] in which case we write [math]f(x) = \mathcal{O}(g(x))[/math] as [math]x \rightarrow a,[/math] what we should be able to do is we say that there should exist positive real numbers [math]M[/math] and [math]\delta[/math] such that [math]|f(x)| \le M|g(x)|,[/math] when [math]0 < |x-a| < \delta.[/math] In other words, if we're sufficiently close to [math]a[/math] but not at [math]a[/math] then we can approximate the quantity [math]\left|\frac{f(x)}{g(x)}\right|[/math] by the positive real number [math]M.[/math] Usually though, we're mostly interested in the case where [math]a = 0[/math] because then we can do nice things with infinitesimally small things etc..

>>8592306
I appreciate your effort and rigour but there are more symbols I don't recognise or fully appreciate. I'm coming at this maths from a physics perspective and they only teach us the maths we most immediately need

File: trollface_infiniteseries.png (110KB, 864x492px) Image search: [Google]

110KB, 864x492px

Check out the trollface on PBS youtube infinite series video. I LOLLED.

File: Screen Shot 2017-01-10 at 19.58.04.png (25KB, 587x143px) Image search: [Google]

25KB, 587x143px

Hey guys,

I'm parsing files (Wiki pages, basically) using the re package in python (might not matter) and I'm having problem with the following. The structure is as such

=== Header1 ===
[[link1]], [[link2]],
[[link3]]
=== Header2 ===
[[link3]]
=== Header3 ===
[[link1]], [[link2]]

This is read in as a STRING, i.e.
STRING = "=== Header1 ===\n[[link1]], [[link2]],\n[[link3]]\n=== Header2 ===\n[[link3]]\n=== Header3 ===\n[[link1]], [[link2]]"

Here the names are dummies. Names and quantity of headers and links is basically random

I'd like to get the data, e.g. in a dict.

d = {"Header1": ["link1", "link2", "link3"], "Header2": ["link3"], "Header1": ["link1", "link2"]}

And here is the reference for the re package I use to try and assemble some code

https://www.tutorialspoint.com/python/python_reg_expressions.htm

File: 1483782323128.jpg (33KB, 960x540px) Image search: [Google]

33KB, 960x540px

Absolute uneducated plebian here, I need help with neuroanatomy and neurotransmitters. My best friend is a unifag and he's under a ton of stress right now, he needs to get an A in this class but he tells me that he doesn't know enough about "neuroanatomy and neurotransmitters". I've only taken biology courses, but I really want to help him out, take away some of the insane stress he's got.

Can any of you recommend some books on the subject I could read, take notes from, then give to him? Hopefully it'll be like he's reading two books at once.

>>8592456
I should mention also that apperently it's a class about drugs and how they affect the mind.

I'm attempting to be an active learner by taking notes from the math textbook that I'm reading, but I want to know the best method of taking notes.

I am already doing all of the practice problems at the end of the book, however I'd like to combine this with an effective note taking method (since I am doing this self-didactically.)

File: Captura de Tela 2017-01-10 às 19.23.22.png (137KB, 890x642px) Image search: [Google]

137KB, 890x642px

Can anybody help me find the azimuthal angle phi in which the planes x-z=0 and z+y=0 intersect? My math is telling me it should be phi=arctan(y/z)=arctan(1)=pi/4 but when I put that into my software it is not quite right, it in fact is tangent to the middle of those planes. The close I got was about 0.95, but I want an exact answer and the math behind it.

>>8592247
jerk off some time before going so that you can stay cool for a while

more of a request, but does anybody have that image where a guy tells how he taught some 4th grader he tutored algebra? If I remember he used things like times tables, gave the kid structure because his mom was always away, etc

File: IMG_1499.jpg (57KB, 640x480px) Image search: [Google]

57KB, 640x480px

>>8591198
Anyone know what this is?
I was just playing some vidya, looked down for some reason and noticed this on my forearms. Both, nearly identical pattern.

Looks like burst blood vessels. I assume I was just sitting weird and blood flow was not ideal or something.

Only time this ever happened was sometimes when I have sex or masturbate my chest flushes. I dont have leukaemia

DO I HAVE CANCER? ITS WHAT GOOGLE TELLS ME

Anybody know of good sites to help get through Physics III course. It's over relativity, quantum mechanics, and nuclear(? vague on syllabus). Anything helps thanks

>>8592646
Anyone?

what does /sci/ have against Stewart calculus?

File: 1484042750235.gif (4MB, 204x204px) Image search: [Google]

4MB, 204x204px

>>8591681
>>8592220
G-g-guys what do you think?
Here's a rare gif for you.

>>8593233
They look like abrasions.
The major blood vessels don't go that way.

Do you get sweaty their often? Does it rub?

>>8593484
I think ilectureonline is pretty good. Haven't used it for physics III though so dunno.

Why does the categorist cross the road?

I'm doing a project with under water water communication. I am using this article as a reference http://file.scirp.org/pdf/JEMAA20110700001_18390291.pdf
I'm confused what conductivity for the water they are using. In the abstract he say average conductivity is 0.01 S/m for fresh water, but in (3) the Debye parameters of water is 17.1 S/m. Any guess what the conductivity of water is being used for the charts?

>>8593745
Thanks bud looks like a useful site

File: 1481538650550.jpg (77KB, 500x497px) Image search: [Google]

77KB, 500x497px

How often are useful contributions made by those who did not go on to grad school (autodidacts)?

I think I'm droppin' outta the race boys

Is (∃x)(¬P(x) ∨ Q(x)) equivalent to (∃x)(P(x) → Q(x))?

freshman cs student here please be nice

>>8593915
TA for logic here, that is correct. My textbook calls that the material conditional rule and the replacement should hold regardless of the main operator. (i'm rusty so if i'm wrong pls don't bully.)

>>8593912
in math specifically, btw

I just don't see going into a PhD being a great idea desu, academia seems to be a big circle jerk and grad students are slave labor tier


what are the objective benefits of grad school? certainly I could learn it all outside of the classroom, right?

>>8593915
P implies Q
is (classically) equivalent to
(not P) or Q
and sometimes "implies" is even defined in that way.

The \exists-spiel is unrelated here, and extra.

File: 2017-01-11-085227_330x283_scrot.png (118KB, 330x283px) Image search: [Google]

118KB, 330x283px

SOMEONE PLS HELP

>>8593995
>>8593921
∃x)(∀y)(¬y = 0 → L(x, y))

What about something like this?

"Suppose our domain of discourse is all natural. Assume L(x, y)
represents the claim “x is less than y.”"

still a little confused about the order of the two quantifiers

>>8594037
Unfortunately my brainlet class doesn't use that notation, maybe the other guy knows. I haven't fallen for the CS meme yet so we didn't work with numbers, just truth values.

>>8594037
I assume there should be parantheses around "y = 0", so that the: ¬ applies to the proposition 'y=0'.

The way to try and comprehend nested qualifiers is to look at them one at a time, so in fact the statement you have said means:

"There exists an x such that:" (∀y)(¬(y = 0) → L(x, y)).

Meaning, that every time we try to substitute a number into y, there exists a number x such that the proposition holds. Now, from what we know about the natural numbers, this is in fact true.

Since the statement is saying, that when y is non-zero, there exists an x such that x is less than y (which is true, if y = 2, then there exists an x less than it, i.e. 0 or 1, if y =1 then x = 0, and so on).

>>8591198
>>8591241

This is correct.

2 questions about hydrogen -

I've read that a protium atom can theoretically decay, so if it were to decay what would it break down to? I've read that quarks cannot just e it by themselves, right?

Also, how come protium is more common that deuterium?

>>8593925
>what are the objective benefits of grad school? certainly I could learn it all outside of the classroom, right?
You _could_. You could probably do it more or less for free. But you won't.

>>8591688
Doesn't seem right. I'll make my scribbles and post hold on.

File: tmp_25891-1893598810.png (196KB, 1123x347px) Image search: [Google]

196KB, 1123x347px

>>8594517
Sorry,no time to solve our right now. Gotta run.

File: 1464439931956.jpg (29KB, 480x474px) Image search: [Google]

29KB, 480x474px

## IMPORTANT ##

Actually I have soon my exam and I don't know much about predicate logic. Can someone mention and link some good ressource(s)? I need to get the basics and the general idea/concepts down, rather fast.

File: IMG_20170111_182456040.jpg (3MB, 4160x2340px) Image search: [Google]

3MB, 4160x2340px

Why does pic related not work. Know I probably made a mistake, just wondering where.

File: summation.png (9KB, 380x506px) Image search: [Google]

9KB, 380x506px

>>8594680
me to haha

You have to change it to [math]\sum_{n=1}^\infty n^s[/math] first before manipulating it, then you can sub back in s as 0 later.
It's valid since it does converge for [math]s < -1[/math].
For example it's equivalent to
[math]\displaystyle \frac{1}{s+1} \frac{d}{dx} \left. \sum_{n=x}^a n^{s+1} \right|_{x=1}[/math]
which you can evaluate at positive integers at the very least.

Anyway when you have the n^s it's clear that the steps you took no longer work, since, for example, 2^s =/= 1^s + 1^s and 3^s =/= 1^s+1^s+1^s and so on.

>>8591396
Wouldnt it just be 20 times 1.1^48?
This is assuming you are never rounding to the nearest whole chicken

File: tmp_25891-1236379434.png (118KB, 1222x394px) Image search: [Google]

118KB, 1222x394px

>>8591396

I know how to do matrix multiplications (with whole numbers at least), but I'm not sure about this one question.

A =
[-1 3]
[4 -2]
[5 0]

B=
[-3 2]
[-4 1]

The question asks me to find the product for a) AB and b) BA. a) is easy enough, but what do I do with b)? It can't just be switching the two around because you can't the columns in 2x2 is less than the rows in 3x2.

Sorry if it's a very stupid question...

>>8595250
the question has to be written wrong

you can only multiply a mxn matrix A with a axb matrix B if a=n (# of columns of first matrix needs to equal # rows of second matrix)

I have a flat 8x6 inch object that weighs a pound. It's rectangular with rounded corners

I need a plausible way for this to generate a small amount of lift enough to cause it to momentarily move upwards if it's moving fast enough horizontally. It can be rotating or spinning or not.

I just need some explanation of how it could have moved in an upward arc and not simply forward and downward

>>8595250

The other anon already answered your question but I'd still like to reiterate, elaborate, and suggest a MNEMONIC.

Consider two matrices [math] Y [/math] and [math] Z [/math] , whose entries are all complexes (that is, complex numbers, of which natural numbers, real numbers and so on, are all specific examples) and thus the crunching is amenable to the usual arithmetic. Let us reiterate along the lines of what the above poster >>8595284 wrote: Let us specify that the number of rows in Y is m, the number of columns in Y is n, the number of rows in Z is a, and the number of columns in Z is b. We may if we wish, write a subscript for any matrix at our convenience, to specify these quantities. By convention, a matrix's number of rows is ALWAYS written first, and a matrix's number of columns is ALWAYS written second. Thus our two matrices can be written as [math] Y_{m \times n} [/math] and [math] Z_{a \times b} [/math] . By definition (hopefully, obviously) all of m, n, a and b are natural numbers.

As the other anon as-good-as-said, matrix multiplication is only defined when the number of COLUMNS in the first (left) matrix, is equal to the number of ROWS in the second (right) matrix. Thus, in order for the the product [math] Y_{m \times n} Z_{a \times b} [/math] to be evaluated, defined, worth doing and not looking stupid in trying, we immediately require that n = a, just as the above anon said. This allows the arithmetic to work out in a well-defined way, you just have to be careful to do your boring bookkeeping while crunching.

FURTHER, continuing with the above, the RESULT of such a matrix multiplication, IS a matrix whose number of rows is EQUAL to the number of rows in the first matrix, and whose number of columns is EQUAL to the number of columns in the second. Thus, if n = a, then the above product is indeed defined, and may be expressed thus, as some matrix [math] W [/math] : [math] Y_{m \times n} Z_{a \times b} = W_{m \times b} [/math]

cont.

If I have a (pseudo)random number generator that outputs numbers uniformly distributed between 0 and 1, how do I play with these numbers so the distribution fits an arbitrary PDF?

I want to study physics. Do you guys knows some good textbooks?

I don't know calculus, but I can learn if necessary, but I don't want to take like 6 months on it

>>8595373

Now for the mnemonic which I recommend to you: if you know to write basic information for matrices out in this way, then you can do a little "cancellation" trick to simplify and know what you're driving towards, ahead of time. Sharper anons should know where I'm going with this.

Continue with the above example, where n = a and the matrix product W is defined. In determining the product W, I like to imagine (as a slight abuse of notation) that the inner two dimensions n and a "cancel", or whatever word you prefer. In any event they "go away" in the course of evaluating W, so that (again, abusing notation), you might write something like:

[math] Y_{m \times a} Z_{a \times b} = Y_{m \times \rlap{/}a} Z_{ \rlap{/}a \times b} = W_{m \times b} [/math]

where I simply replaced n with a because, after all, they're equal and you could have done the other if you'd pleased. As you see in my notation, the two inner dimensions "vanish", and the real point of this type of activity (which is so dumb-simple that it can of course be done mentally once you understand the motivation, which is to have a clear idea of what a matrix product is going to look like in terms of dimensions) is simply to look at what's in front of you and figure out whether what is proposed is a defined multiplication, or a trick question where the proper homework response would be "undefined".

Let us now turn this elaboration to the concrete example. You provide [math] A , B [/math] and are asked to evaluate AB and BA. We have

[math] A_{3 \times \rlap{/}2} B_{ \rlap{/}2 \times 2} = C_{3 \times 2} [/math]

[math] B_{2 \times 2} A_{3 \times 2} [/math] is undefined, as [math] 3 \neq 2 [/math] .

I don't recommend writing the mnemonic down on a homework assignment (a professor might be pedantic about it), just use it mentally. The above is how you answer this type of question properly - there is sufficient context in the line for the professor to be confident that you get it.

do those buttons at crosswalks actually do anything? the ones you press when you want to walk across

in my personal experience they never seem to reduce the timespan between light changes

>>8592646
A-a-anyone? ;__;

>>8594735
>>8594680

You cant subtract infinity from inifinty

>>8595416
at (relatively) busy crossings no, they are purely placebo. infrastructure planning is tough to get right, why would a city planner say "eh fuck all the logic behind how i designed this intersection, let the pedestrians always have priority", especially on a major street?

on smaller streets where there may not be much traffic (or rather, where traffic is very variable, for example a residential area where people go to work at 9 and come back at 5, but almost no cars in between), the buttons are pretty much guaranteed to let you through real soon.

Is a natural law (ex. the speed of light) comparable to a school schedule in terms of how it could change? Related to uniformitarianism.

>>8593915
>9
look at the truth tables and see for yourself jackass

>>8595438
You usually do not need to take notes as if it were some life science course. Do the exercises and when you get stuck, that is what the handful of examples in each section are for.

is the product of two hermitian operators itself hermitian?

I want to be a badass chemist. Which upper year chemistry courses are necessary for this? I'm assuming Organic and Biochemistry are mandatory since those are prerequisites for everything.

>>8595587
If your only good skill is memorization, then you should be in /his/.
looks like someone failed their logic class and realized that computer science isn't vidyagame making degree. go to /a/

>>8595689
are you not already a chem major at your uni? organic is like intro chem for chem majors. even after undergrad and you take some higher level courses you've still got a long ass way to go.

study hard in your physics and math classes so you don't die in physical chemistry. learn programming because computation is really important. you kind of sound like either a freshman or someone who just finished breaking bad

I need to combine linear falloff of explosion force with distance and inverse square falloff of explosion force with distance.

Obviously it's impossible to have true inverse square that is zero when distance = blast radius, but what would be a good imitation?

The points (1, 3) and (−2, 6) lie on a line. Where does the line cross the x-axis?

Ik how to do this easily with y =mx+b, but I'm in a linear algebra course and I need to do it using a matrix.

I set up the matrix
1 -2
3 6
But then what? If I try to make it go to reduce form, it just becomes
1 0
0 1

>>8595889
you have the equations
3=m+b
6=-2m+b

so the matrix equation is
[1 1][m]=[3]
[-2 1][b]=[6]

invert the matrix on the left to solve for the vector
[m]
[b]

>>8595889
or i guess you want to solve
(1,3)+t[(1,3)-(-2,6)]=(x,0)
(1,3)+t(3,-3)=(x,0)
(1+3t, 3-3t)=(x,0)
so need t=1
so x=4

>>8595250
Watch this entire series.

https://www.youtube.com/watch?v=kjBOesZCoqc&list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab

>>8595894
Thanks, this helped

What about something like this?
"The points (3, −1, −5), (1, 4, 14), and (5, 3, 3) lie on a unique plane. Where does this plane cross the z-axis?"

I got the answer as z = 4 but I had to use vectors and cross products (I'm supposed to use matrices in linear alg or something else, not cross product).

I tried setting up a matrix in the form

ax + by + cz + d = 0

1 4 14 1 0
3 -1 -5 1 0
5 3 3 1 0

But I think I did it wrong.

I then tried again without the zeroes at the end (ax + by +cz = d) and I got nice looking answers (a = 1/2, b = -3/4, c = 1/4, but I'm not sure what to do with those answers)

>>8595950
>(3, −1, −5), (1, 4, 14), and (5, 3, 3)
you can write
(0,0,z)=(3,-1,5)+t[(3,-1,5)-(1,4,14)]+u[(3,-1,-5)-(5,3,3)]

use the first two equations to solve for t and u, then substitute it in to get z=4

File: 220px-Sphere_with_chart.svg.png (25KB, 220x355px) Image search: [Google]

25KB, 220x355px

just looking for a hint, not a solution

given a continuous function f from the unit sphere embedded in R^3 to R, show there exists an orthonormal basis u1,u2,u3 of R^3 with f(u1)=f(u2)=f(u3)

i can do it when its a function f(theta):[0,2pi] to R from the unit circle in R^2 instead of the sphere in R^3 but i don't know if the proof is adaptable.

an orthonormal basis u1, u2 in R^2 has a pi/2 angle between them so we can consider the function f(theta)-f(theta+pi/2)

since the circle is compact f has a maximum u and a minimum v

these satisfy f(u)-f(u+pi/2)>0 and f(v)-f(v+pi/2)<0, so by continuity there exists w with f(w)-f(w+pi/2)=0 and so the vectors corresponding to w and w+pi/4 are an orthonormal basis of R^2

>>8595392
Use the inverse of the CDF (inverse transform sampling).

>>8595820
Inverse-square minus a constant.

File: 21815_v3_122_583lo.jpg (159KB, 1000x680px) Image search: [Google]

159KB, 1000x680px

What pressure/temperature calls for the Van der Waals equation be used instead of the ideal gas law? I'm looking for some rule of thumb but I can't find anything.

What does ITT mean?

>>8596299
IT = Internet Technology
ITT = IT Technology

>>8596304
I see people us ITT on here and it don't think they are talking about IT technology

>>8596114
I don't understand the question. Are you saying you are to prove that [math]\forall f\in \{g \in \mathcal{C}(\overline{B_1(\mathbb{0_3})}) : g(\overline{B_1(\mathbb{0}_3)}) \subseteq \overline{B_1(\mathbb{0}_2)}\}: \exists \mathbb{u}_1, \mathbb{u}_2, \mathbb{u}_3 \in \mathbb{R}^3 : <\mathbb{u}_i,\mathbb{u}_j> = \delta_{ij} \; \forall (i,j) \in \{1,2,3\}^2 : \text{Span}\{\mathbb{u}_1,\mathbb{u}_2,\mathbb{u}_3\} = \mathbb{R}^3 : f(\mathbb{u}_1) = f(\mathbb{u}_2) = f(\mathbb{u}_3),[/math] where [math]\mathbb{0}_n[/math] is the [math]n\times 1[/math] vector comprising of only zeros, [math]B_r(\mathbb{x})[/math] is the ball of radius [math]r[/math] around the point [math]\mathbb{x}[/math], [math]\overline{E}[/math] is the closure of the set [math]E, [/math] [math]\mathcal{C}(E)[/math] is the set of all continuous functions defined on [math]E[/math] and [math]\delta_{ij} = \begin{cases} 1 \text{ if } i = j \\ 0 \text{ if } i \neq j\end{cases}?[/math] Please clarify.

Also, I'm sorry for being so rigour here but I really need to know exactly what you need to prove in order to give you a hint.

Just failed my exams in calculus and linear algebra, is it time to kill myself?

>>8595648
if and only if they commute

>>8596389
yes

File: slightly overlapping charged plates.png (64KB, 1087x749px) Image search: [Google]

64KB, 1087x749px

>>8591198
This are oppositely charged plates that slightly overlap.

How can I conceptually see that the red parts are none zero?

I ask because I don't understand why we can assume that a point in (l,w) will experience the entire force calculated for the area of l*w. Doesn't every point only experience the force acted upon it's infinitely small area?

>>8596299
>>8596305
in this thread:

>>8596389
No. Never give up.

What is the name of the field that study functions like zeta, gamma and beta and what are good introductions to it ?

>>8595950
Matrixes are just a form of notation. Not only are solving a system of equations mathematically equivalent to row-reducing a matrix. They are exactly the same in every sense but notation. You basically just ommit x,y,z and write them in a block.

Write down all equations.
Turn these into a matrix.
Row-reduce (Gaussian elimination, in practise usually done with computer for speed, but easily done by hand too)
Write down the equations you have now (normally you don't do this, but easier to visualize for a beginner) with added variable parameter for unknowns in the same colomn.

Gongrats, you now did exactly the same as if you used a classic substitution only faster and compacter.

>>8596483
>>8596522
Alright, as there are opposing views on this I'll hold on one more semester.

>>8596529
If you want I can even tutor you a bit during the summer :) Just give me your skype if interested. Regardless, never give up. You can do it!

>>8594820
lmao compound chickens

>>8596294
You use the ideal gas law for (preferably monoatomic) gasses at low density (high volume, low pressure). Within these bounds IGL is usually sufficiently accurate for everyday applications.

The Van der Waals equation is an improvement of the IGL that doesn't have said limitations. However it is still inaccurate for gasses close to the gas-liquid equilibrium line.

>>8596294
>>8596547
Oh I'm sorry, seems that I misread you question.

Well, I've personally never heard of a rule of thumb for this. It depends on the Van der Waals constant of the particular gas. If you're really unsure if a particular setup crosses the line you can always look up the constants and calculate if the difference is negligible or not.

>>8591198
What does "+" sign signify in complex number like
2+3i.
What is the meaning of + here. Does it add 2(a real number) to 3i(an imaginary number).

>>8596559
2(a real number) + 3i(an imaginary number) = 2+3i(an imaginary number).

>>8596559
What the complex number [math]z=2+3i[/math] actually means is on the complex number plane, we want to first go two positive units on the real axis and then three positive units on the imaginary axis. It's the same as vector addition, really. Your interpretation is also correct, since [math](2 + 0i) + (0 + 3i) = 2 + (0i + 0) + 3i = 2 + (0 + 0i) + 3i = (2+0) + (0i+3i) = (2+0) + (3i+0i) = (2+0) + (3+0)i = 2+3i.[/math] This is a consequence of how one can define equality in [math]\mathbb{C},[/math] namely that we say that [math]z, w \in \mathbb{C}[/math] are equal if and only if [math](\Re(z) = \Re(w)) \land (\Im(z) = \Im(w)).[/math] That is to say, we first go an equal amount of units in the same distance on the real number line, and then deviate from the real number line by going the same amount of units in the same direction parallel to the imaginary line. But here's the thing, you can't actually remove that plus there. It's an indication, an instruction to do MORE once you're done with what you've been instructed to do on the real line.

>>8592211
Big O notation. Basically saying "any further orders can be ignored because they are higher orders of an infinitesimally small variable". Obviously you can only use this if you keep the last used order in your formula (in this case 1). If for example you want to make a statement about
(right side of 4.4) - dF/dx delta x^2
than you obviously can't use the O(delta (x^2)) notation, because now it is now order 2 is no longer negligible*.

* by which I don't mean approximately negligible, but actually negligible

Basically it all comes down to limit x->0 (ax+bx^2+cx^3) = ax

>>8596559
Think of a classic 2D graph with x-axis and y-axis

the x-axis (all real numbers) is a line that occupies 1 dimension
so any point x can be represented by 1 real number
the y-axis (all real numbers) is a line that occupies 1 dimension
so any point x can be represented by 1 real number
a point (x_0,y_0) is a line that occupies 2 dimensions (doesn't have to lay on any of the two axis lines
so any point x can be represented by 2 real numbers

Now, how do we represent an imaginary number? Simple
z = a+bi
So how many real numbers do we need to represent an imaginary number? 2: a and b.
So what is the difference between visually representing a point (x_0, y_0) and an imaginary number? Nothing.
You can just call a=x_0 and b=y_0 and represent any imaginary number on an x,y graph.

Really let this sink in: any imaginary number can be represented by 2 LINEAIRY INDEPENDENT* REAL numbers. Any imaginary number is just a point on a 2 dimensional plane with axes "real" and "imaginary".

*You cannot write i as a linear function of 1.
*You cannot write 1 as a linear function of i.

There is NO difference between saying z = ax+by and a =a*1+b*i. Because just as x and y are linearly independent and span a 2D space, 1 and i are linearly independent and span a 2D space.

------------------------------

So what does the "+" do? It's just a plus. It's doing exactly the same as the plus in "ax+by" is doing: adding two linearly independent real numbers.

>>8595331
If you just want it to move upwards for a few moments, then obviously just move it forward at an angle for which the upward force caused by the air resistance is higher than the weight of the object and the downward force caused by drag.

Calculating these things for your object can be done the quickest and easiest by looking up the drag coefficients for your specific shape.

If I have a certain PDF, for example
> 3x^2 if 0 < x < 1
> 0 otherwise
can I simply say that the CDF is x^3, or should I also specify its value when x is not between 0 and 1?

>>8596675
Yes, because there's zero probability of ever obtaining a value in that range; that is, [math]\mathbb{P}(X < 0) = \mathbb{P}(X > 1) = 0.[/math] So it would be incorrect to NOT write [math]F_X(x) = \begin{cases} x^3 \text{ if } x \in(0,1) \\ 0 \text{ if } x\notin(0,1)\end{cases}.[/math]

File: 9879498.jpg (73KB, 320x240px) Image search: [Google]

73KB, 320x240px

Ok.
This is a really stupid question.

--------------------------------------------------------

Consider the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.
With them it is possible to assemble a number "a, b, c, d, e, f, g, h, i, j".

(Each letter represents a different number) so that:

"a" are a number divisible by 1;
"ab" are a number divisible by 2;
"abc" are a number divisible by 3;
"abcd" are a number divisible by 4;
...
"a, b, c, d, e, f, g, h, i, j" are a number divisible by 10.

Find the value of "a, b, c, d, e, f, g, h, i, j".

--------------------------------------------------------

Sure, lets go.
In solve say:

--------------------------------------

The "abcd" number must be divisible by 4, which means that "cd" is divisible by 4.
Thus "cd" is 12, 16, 32, 36, 72, 76, 92 or 96.
Therefore, d is worth 2 or 6.

-------------------------------------------------

Why?
Seriously, why?
Why "12, 16, 32, 36, 72, 76, 92, 96"?
Why not "20, 28, 40" or any number between "36" and "96"?
What property I dont see?

I'm trying to show that if [math] H [/math] is not Hermitian, then [math] H ^{ \dagger } H [/math] is Hermitian with non-negative eigenvalues. I've broken it down into two parts, showing that [math] [math] H ^{ \dagger } H [/math] is Hermitian and then showing that it has non-negative, real, eigenvalues. The second part is easy. However I'm having trouble with the first part. It seems so blindingly obvious, if [math] H ^{ \dagger } H \neq \left ( H ^{ \dagger } H \right ) ^{ \dagger } [/math] then that would imply that [math] H ^{ \dagger } H \neq H ^{ \dagger } H [/math] But then I've not use the hypothesis of H being non-hermitian, is that just redundant?

File: thumbnail_attachement.png (12KB, 456x511px) Image search: [Google]

12KB, 456x511px

Time for the obligatory 'this question is fucking stupid but'. This is a statistics question also

Anyhoo, I'm trying to look this hypothesis: Turnout tends to be higher in proportional representation electoral systems. I've got the data variables for these, and I've put them into stata and crosstabbed em'.

So now I'm trying to think what I can do that demonstrates the statistical significance here. Is there a stata command that can separate the two sets of results so I can compare? I imagine there's something else I could do to compare significance, but thread for stupid questions so.

File: me dumb.png (3KB, 268x103px) Image search: [Google]

3KB, 268x103px

Not gonna lie, this is probably really easy and it's just something I either forgot or am not getting. It's been a while since I went over some of this stuff.

I'm not so much interested in what the answer is, more in how to get to the answer so I'll know how to solve these types of problems.

With that said, I'm really drawing a blank here. I know how to rationalize the numerator, I'm just not sure what to do with the denominator. When I rationalize the numerator, I get 2x+h. But I'm not sure how the bottom changes when multiplied by sqr x + sqr x +h.

>>8596755
Here are two hints: [math]\sqrt{xy} = \sqrt{x}\sqrt{y},[/math] [math]\sqrt{\frac{x}{y}} = \frac{\sqrt{x}}{\sqrt{y}}.[/math] Also, the distributive law still holds true even if you are working with square roots. If you get stuck, come back and ask again.

File: 1474107946054.png (4KB, 240x178px) Image search: [Google]

4KB, 240x178px

More venting than asking a question but

>Despite somewhat consistently turning in some shit late last semester, professor asks me if I wanted to do some research with her
>agree immediately
>she wanted me to do some stuff this winter break before the semester started, to catch up on material
>promise myself I won't finish late so as not to disappoint her again

>4 days into semester
>still haven't finished the shit
>emails me today asking if i'm still alive

i'm scared bros
i fucked up already, I didn't want to disappoint. This may have been my only chance at doing research. I'm so scared that she's going to drop me. I'm rushing to finish what she wanted but fuuuuuck. feeling so much shame right now.

File: WIZARDY.gif (144KB, 126x126px) Image search: [Google]

144KB, 126x126px

>>8596818
>mfw I'm not you

>>8596818
not your blog faggot
>>>/r9k/

>>8596726
You basically want the proof that there exists no combination of natural numbers a,b,c,k with
a = element of {1,2,3,4,5,6,7,8,9}
b = element of {2,4,6,8}
c = element of {2,4,5,6}

a*100+b*10+c=k*3
or alternatively
a+b+c = k*3

(the sum of the digits of a 3-digit number is divisible by 3 if and only if the number itself is divisible by 3)

That leaves us with 9*3*4= 108 combinations for which to check whether k is natural.

Sorry, I don't see a quicker way to do this. But I'm curious whether there is.

>>8596807
>>8596755
Probably not relevant for you question, but just in case: those only apply if x and y are real numbers.

>>8596901
I see that I wrote a 3 instead of a 4. Probably made a few more mistakes, I'm tired.

>>8596907
The question is just to rationalize the numerator. I can do that easily, however, the denominator is what's confusing me.

Am I working it correctly by multiplying the sqr x by the sqr x+h in the denominator? As in, changing the denominator to hx(sqr)hx before multiply by the conjugate of the numerator? Like I said, it's been a while sense I tackled radicals, so I'm very rusty. I'm assuming the x and x+h in the original denominator can be combined for x^2, thereby removing it from under the radical and giving hx(sqr)hx. Though, I could be completely wrong about that. And even if I'm correct, there's still the matter of multiplying in the conjugate.

File: 1483751315102.jpg (7KB, 250x242px) Image search: [Google]

7KB, 250x242px

Final bump.
Is this
>>8591681
A correction or confirmation (I can't understand the anons writing) of

>>8591357
>>8591360
>>8591361
>>8591364
>>8591366
>>8591370

I don't even know if I'm asking this correctly but
given f(x,y,z) = dx/dt, what is a way to find f'(x,y,z) in the same way as
dy/dx = f(x,y)
f'(x,y) = df(x,y)/dx + df(x,y)/dy *(dy/dx)
but now with an extra variable

File: 20170112_201231.jpg (3MB, 1967x3151px) Image search: [Google]

3MB, 1967x3151px

Why does my y=1 value give ne two values for x?

:^)

>>8596962
If the function you're describing is f(x(t),y(t),z(t)) and you want de take the derivative with respect to t than you get
df/dt = df(x(t),y(t),z(t))/dx*dx/dt+df(x(t),y(t),z(t))/dy*dy/dt+df(x(t),y(t),z(t))/dz*dz/dt.

>>8596968
x^2 = 1 has two solutions
x=1 and x=-1

1^2 = 1
(-1)^2 = 1

Or in general:
x^2=y <=> x=+sqrt(y) or -sqrt(y)
The sqrt of any real number >=0 is always defined to be >=0

>>8596916
If you write your reasoning out I'll have a look.

>>8593915
NOT(A) OR B = TRUE
X OR Y = NOT( NOT(X) AND NOT(Y) )

NOT( A AND NOT(B) ) = TRUE
A AND NOT(B) = FALSE

So B can never be false if A is false

ergo A->B

>>8597008
*if A is true, I meant

File: Screenshot_947.png (30KB, 942x530px) Image search: [Google]

30KB, 942x530px

Anyone able to help me understand where the 2 in -2k(lambda)/R came from?

I was able to follow until there.

>>8597033
[math] \lambda [/math] is normally linear charge density, defined as charge per unit length: [eqn] \frac { d q } { d l } = \lambda [/eqn]

File: problem.png (62KB, 2394x1091px) Image search: [Google]

62KB, 2394x1091px

>>8596993
This is essentially how I'm thinking to go about it. Like I said, it's been a while so I don't clearly remember exactly what I need to do.

>>8597033
>>8597038
Oh sorry my bad, that just comes from the integral over [math] \int ^{ \pi } _{0}\sin ( \theta ) = 2 [/math]

>>8597048
First of all, I'm assuming h is the imaginary number and x is real?

on the left side, third to last line you say that
h*sqrt(x^2+hx) = h*x*sqrt(hx)
What makes you think that's true?

I have to be honest. These notes are a bit of a clusterfuck to read. Can you make a simple vertical logical deduction please.

>>8597071
That's how the problem was presented to me, only with instructions to solve by rationalizing the numerator. I'm not sure why I'm even obsessing over this one problem so much, I got every other question right, it's just this one I don't understand and it bothers me.

I assumed that since the bottom is h times sqrt of x times sqrt of x+h, that I could simplify it by combining the two squares, thereby making sqrt x^2 +hx, and since the x is squared it can be removed, hence hx sqrt hx. That's the line of thought I used to get there.

>>8597086
The error in your thinking is that
sqrt(a^2+b) = a*sqrt(b)
is NOT true.

You're confusing addition with multiplication:
what is true is that
sqrt(a^2*b) = a*sqrt(b)

See "*" not "+".

>>8597090
The second is true because
sqrt (a*b)= sqrt(a)*sqrt(b)

The second implies that
sqrt (a+b)= sqrt(a)*sqrt(b)
which is obviously not true since both of them combined imply that
sqrt(a+b)=sqrt(a*b)

so that's like saying sqrt(1+3) = sqrt(1*3).
So 2 would be = 1.73205080757
You see, not true.

how do you measure the distance between two events in galilean spacetime?

is it
[math]d^2 = x^2 + y^2 + z^2[/math]

or

[math]d^2 = x^2 + y^2 + z^2 + t^2[/math]

File: 068746464.jpg (88KB, 564x789px) Image search: [Google]

88KB, 564x789px

>>8596901
>>8596912

>You basically want the proof that there exists no combination of natural numbers a,b,c,k

Yep.

>That leaves us with 9*3*4= 108 combinations for which to check whether k is natural.

I see.
I just wanted understand the method.
Because, for me, that numbers only "appear from limbo".

Thanks, anon.

>>8597050
>8597050
But, where does the d theta go then? Sory for late reply, had a tutorial

How do I stop overthinking? Most of the time, when I overthink, its due to my perception that either the teacher is trying to trick us, or "it can't be that easy". Did anyone else experience compulsive over-thinking?

My only experience with calculus was a course I took back in high school roughly 2 years ago. I still remember more or less how the concepts covered there worked, but I'd like to get more in to calculus and maths in general.

Is Spivak's Calculus a decent jumping off point for someone like me, or do I need to read like, a lower level introductory book first?

>>8597242
Simple, drill basic logic and your fucking course material into your brain.
Then, if your argument follows from the course material using basic logic, then it works, period.

>>8597211
You've turned the integral of dE into an integral of dtheta.

>>8597249
Try Paul's Online Notes to get a feeling for what level you're at. Then you can pick up virtually any calculus book you want, as long as it's not an analysis book since you're probably not ready for that kind of rigor yet.

>>8597430
Cool thanks anon.

"Shift" an equilibrium reaction to one side or the other.

What did all my chemistry homework mean by this?

Can I refer to points on a Cartesian plane as "planar points," or are planar points something completely different?

I like the sound of it more than points on a plane, but wolfram says it's some sort of complicated shit.

>>8597494
suppose you have a + b <-> c + d in equilibrium

say if you were to add a, the reaction will shift to the right as it starts to reduce a, and by doing so uses b, and makes more c and d

>>8596731
yes, [math] A^{ \dagger } A[/math] is Hermetian for any A.

File: Untitled.png (66KB, 1672x736px) Image search: [Google]

66KB, 1672x736px

Why do people thing accounting is boring? This is pretty intensive for me.

>>8591198
the fuck are all these crazy symbols

>>8597615

In general, you don't need to emphasize "planar points". You should ignore the Wolfram article for the moment - it simply describes a precise technical term that is used in higher math, which is not immediately related to your concerns, like how "work" has a precise definition in physics, despite having "natural language" connotations as well. Basically what happened in both cases is that scientists and mathematicians knew about some abstract thing, and they had to assign some word to it, so they took their best shot and re-used words that have other common meanings, which are a bit more different and precise in their usages.

The basic idea of a (EUCLIDIAN) plane hasn't changed significantly for the past few thousand years. Humans basically understand what it /is/, or is supposed to be, but there are a few significantly mathematically different ways of modeling a plane, which have other applications.

There are three "Euclidian" models which amount to the same plane, that I am aware of:

The Euclidian plane itself, which does not imply any particular coordinates apart from those immediately under discussion (and is not directly linked to algebra),

The Cartesian Plane, which is the exact same thing except that every point is now assigned a rectilinear two-dimensional coordinate, and this, together with algebra, makes possible explicit illustration of algebraic ideas as being coterminous with a certain geometry, in a more elaborate and general fashion than Euclid himself had managed,

And then there's the Complex Plane, which preserves the basic Cartesian idea, except we now have distinct, more general algebraic mathematical objects that have different rules. See the "Argand Diagram" for a 1-1 correspondence between this model and the above cartesian one.

These three are variations on the same one theme, put toward certain different ends.

say I have sequence x0=0 and xn+1=(xn^2 + 2)/sqrt(2)*2

how the fuck do I prove its upper bound is sqrt(2) (which it is)

File: 1239555_567613286687056_8362566405684053897_n.jpg (15KB, 261x194px) Image search: [Google]

15KB, 261x194px

I just did a grammar test and got a couple wrong.

>I didn't watch TV last week.
Sure, "I haven't watched" would be better, but is this sentense really incorrect?

>We don't want to have dinner in that restaurant.
The fuck is this? All I could this of is "at that restaurant" instead of "in", but that seems like bullshit and I feel like I am missing something.

>>8597784
> x[n+1]=(x[n]^2 + 2)/(2*sqrt(2))
=> x[n+1]-x[n]
= (x[n]^2 + 2)/(2*sqrt(2))-x[n]
= (x[n]^2 - 2*sqrt(2)*x[n] + 2)/(2*sqrt(2))
= (x[n]-sqrt(2))^2/(2*sqrt(2))

That indicates that, if it converges, it converges to sqrt(2). But that doesn't automatically mean that it converges or that it never overshoots.

For that, you'd also need to show that the difference x[n+1]-x[n] < sqrt(2)-x[n]. For x[0]=0, x[n+1]-x[n]=sqrt(2)^2/(2*sqrt(2)) = 2/(2*sqrt(2)) = 1/sqrt(2) < sqrt(2). Thereafter, as x[n] increases, |x[n]-sqrt(2)| decreases.

can someone tell me when or where least common multiple is ever useful

File: 1888756_206213559577085_711513893_n.jpg (9KB, 500x281px) Image search: [Google]

9KB, 500x281px

>>8597784
>>8597906

How do you know exactly which part of math that is and the proper way to solve?

File: Screen Shot 2017-01-12 at 9.50.45 PM.png (41KB, 1400x142px) Image search: [Google]

41KB, 1400x142px

I have no idea how to even start approaching the problem in pic related...

I now that for example if b == 2, then P (|a-b| > 3) is the same as P ( a > 1 ), which is 2/3... I know the answer is 1/3, but would this be a result of there being a linear relationship (as b increases by .1, a must also increase by .1) and you simply take the average of it?

I'm unsure how I would do this with simply P(Event) = # successes / # trials (seeing as though the number line is infinitely divisible)

>>8597907
Fractions! Specifically, adding them... I'm sure there are tons of uses, but that's the first one that popped up.

>>8597905
Grammar is esoteric.

Either of those in dialogue are fine. Yet the case could be made that they are formally grammatically wrong.
It's not a science.

>>8597911
That's what I thought. I think you are to suppose you can only move in wholes. so 9 possibilities with 3 winners.

>>8597911
This is the continuous case, so you'll need to use integration to solve this.

File: 15265_477509295721409_3682687888124771963_n.jpg (45KB, 441x395px) Image search: [Google]

45KB, 441x395px

>>8597917
This exactly what niggers tell me after I correct theirs.
we wuz kangs

>>8597925
>Integration to solve this

How so?

File: Well Okay!.gif (794KB, 200x281px) Image search: [Google]

794KB, 200x281px

>>8597925
Okay sort of got it now!

I did a "b vs a" chart and plotted a line above which |b - a| > 3... I took the area of that, divided it by the total area, and I got 1/3, which is the answer!

Would you do it a different way? I mean, integration can be used to find area, so I assume the methodologies are similar

>>8597933
They tell you grammar isn't a science?

The first one I'm not convinced is wrong. I think in order to use "haven't" the present tense version of the word needs to use "have".

The second one you could argue either way depending on context.

>>8597945
There's an infinite number of possibilities. It's pointless to assume that this question is asking anything other than whole numbers.

File: 14390929_343495542649408_7488422832466989554_n.jpg (67KB, 600x840px) Image search: [Google]

67KB, 600x840px

>>8597948
They tell me that that as long as the other party understands, everything is ok.
I say let's go back to waving hands as a means of communication.

>The second one you could argue either way depending on context.
What possibly could a different context? Elaborate.
I believe that because logically you are IN a restaurant so it doesn't seem wrong. Tho I agree that oficially would be "at" cuz inglish and rulez and shieet.

>>8591279
>>8591275
>>8591250
What are you guys talking about? The repetition of the word sheaf is delightful to read.

>>8593925
Well, statistically, a fresh PhD is better off than a fresh undergrad. The key word is fresh. I think actually PhDs may earn more money over their entire life but I'm less sure of that stronger claim.

>>8597976
A presheaf (in the less general sense) associates to each open subset of a topological space, a set (often with additional structure) of "sections" (think functions) on that subset.

A sheaf is a presheaf where local sections can glue together to define a unique global section.

Most geometric spaces can be described as a topological space together with a "sheaf of commutative rings" on that space.

Can I post pictures of my genitals on /sci/ if it comes from a feeling of deep emotional connection with this board?

the more dice rolls you combine, the more similar the probability distribution gets to a normal distribution

if for example the height in a human population is normally distributed, then does that imply anything about the "probability" at the individual level? by only looking at the statistics, can you infer that it's more likely that a person will be of average height or could it be more like a dice roll where each height within a certain range is equally likely?

>>8598163 (Me)
i guess if you only look at the mean you can't tell the difference but like if you compare the occurrences of 1,2,3 etc you get different results (that each dice roll is equally common but not so with heights)?

>>8597906
>= (x[n]-sqrt(2))^2/(2*sqrt(2))
>That indicates that, if it converges, it converges to sqrt(2).

w8 how
limn->inf x[n+1]-x(x[n]-sqrt(2))^2/(2*sqrt(2))
=> 0 = (x[n] - sqrt(2))^2
which gives x[n]=sqrt(2)

like this?

>>8597910
I don't understand the question
It's analysis, sequences, and basically try to apply different kind of convergence tests, function proprieties, bounds, etc.
You can find a good amount of theory and examples online, see for example
http://tutorial.math.lamar.edu/Classes/CalcII/Sequences.aspx

>>8596750
Bumping this

File: tbraintlet.png (193KB, 969x796px) Image search: [Google]

193KB, 969x796px

i don't get this proof of the geometric/arithmetic mean inequality. i can follow it up until the last sentence.

>>8598232
x[n+1]-x[n] = (x[n]-sqrt(2))^2/(2*sqrt(2))
So x[n]=sqrt(2) => x[n+1]-x[n]=0 => x[n+1]=x[n]
IOW, x[n]=sqrt(2) => x[n+1]=sqrt(2) => x[n+2]=sqrt(2) => ...

The difference between adjacent terms x[n] and x[n+1] is proportional to (x[n]-sqrt(2))^2. So the closer x[n] gets to sqrt(2), the less x[n+1] will differ from x[n].

Also, (x[n]-sqrt(2))^2 is always positive, so the sequence is monotonic increasing.

So it can't converge to anything other than sqrt(2), and it can't converge while oscillate above and below sqrt(2) (if it ever goes above sqrt(2), it will keep increasing, and increase by larger amounts each step).

So it boils down to showing that for x[0]=0, it converges. Note that for x[0]>sqrt(2) it will diverge. And for x[0] below some value, x[1] may be greater than sqrt(2) (i.e. it will overshoot), in which case it will diverge.

>>8598428
>i can follow it up until the last sentence.
Well, the second to last sentence, alpha is positive.

Then a_1 is smaller than alpha, so alpha minus a_1 is positive.

Then a_n is larger than alpha, so a_n - a is positive

So that entire fraction is positive. So you are substracting a positive quantity out of a_1 + a_n, which means you are making it smaller

Which means that if you took away that substraction then what you would get would be larger (most of the time) or equal (in the case the numerator happened to be 0).

>>8598472
sorry i meant the
>Repeating this process until all the values...
part

>>8598448
Isn't it enough just to do a simple limn->inf, from the beginning? That is

limn->inf x[n+1]=(x[n]^2 + 2)/2*sqrt(2)
Which simply gives sqrt(2)?

does "the poincare group has trivial cohomology" imply the conservation of mass?

I'm taking electricity and magnetism this semester. What concepts do I need to know from mechanics? I didn't do so well with the second half of the course

Is there any symbol for specifying that a value is just somewhere in the area of something without specifying a precision?

>>8599095
You could say [math]n\in [a,b][/math]

>>8599095
approximately or approximately equal to

>>8599022
Be very comfortable with calculus, especially integration. It's possible to do most EM courses with Calc II, but Calc III is recommended to fully understand.
In terms of mechanics, just be comfortable with forces and rotational/Torque. Mostly linear forces.

>>8596389
get ur phd in physics THEN kys

>>8599022
If you understood the differential magic that happened while you were learning moment of inertia, you'll do fine.

>>8599147
so there's a lot of torque in EM?

sorry for this dumb question
I have 78 cards
there are 22 "special cards"
what are the (%) odds to pull 2 special cards in a row

>>8599335
that's really simple man

(22/78) * (21/77)

it's about 7.6%

>>8599335
Do you shuffle your first pull back into the deck before making your second pull?

>>8599374
no

seriously though why do normies have such a hard on for Tesla?

>>8591198

can you do newtons method in 3d

Im doing a ray tracer and I need to minimize a distance equation numerically for hit detection

Scientifically why is /pol/ so stupid?

File: 1482461344646.jpg (19KB, 400x400px) Image search: [Google]

19KB, 400x400px

>>8599448
>sci cuck
kys

>>8599448
only brainlets have the time, energy and motivation to shitpost about politics and related topics on a mongolian ice sculpting forum

File: 1481925852299.jpg (263KB, 764x551px) Image search: [Google]

263KB, 764x551px

>>8599459
>to smart to have any free time for shitpost

>>8599448
probably because you're not redpilled enough to understand the truth

>>8597770
0_0 damn anon. This is probably one of the greatest replies I've had on 4chan.

>>8591198

Motherfucking linear algebra kills me

things like "find the intersect of a line that passes through 0,0,0 that is represented as a vector of 3 slopes and another line that passes through a point and is orthogonal to it" take me a week.

how do I get better? how can I improve?

>>8593233
This might be a long shot, but do you have a low platelet count? If you're right about burst blood vessels, that could be a line of petechiae.

>>8596726
there's exactly one solution, i can give it if you like

>>8599727
>how do I get better? how can I improve?

practise and understanding the underlying concepts (and not just plug and chug formulas) would do the trick would i say

maybe drawing to make the problem more visual is helping you as well
https://en.wikipedia.org/wiki/How_to_Solve_It

Okay, I need some actual advice and not retarded broscience advice:

I am about to start on a reduced meat more vegetarian diet and I am curious about how I should go about it. I am cooking for two people (or three depending) so it's a bit hard to premeasure things like i thought about doing as a way to control the calories down to an approximate amount.

It also sucks though because I don't like the taste of a lot of vegetables and I am allergic to tree nuts so I am going to have to restrict myself even more. Rambling.

Should I still try to measure out the portions or just wing it?

>>8596726
Couldn't you just do the product? a=1, b=2, ... j=10, a is divisible by 1, b is divisible by 2, and it follows trivially that ab is divisible by b, and abcd is divisible by b. So wouldn't abc...hij = 10! (factorial)?

>>8599870
Well it sounds like you should eat less meat

>>8599948

You're right. I just want to fit into a coat I bought online (and also be healthier).

Would it be possible to go into industry for a while and then pursue a PhD later in life? I'm EE/Physics right now and want to know if getting accepted would be harder

File: 1481826007066.jpg (35KB, 552x708px) Image search: [Google]

35KB, 552x708px

>>8599870
> I don't like the taste
> alergic to nuts
beta male, will not survive the winter

how do you measure distance in galilean spacetime?

>>8596731
I'm going to use stars for the conjugate transpose and avoid using latex because I'm a pleb. Basically, you have to remember the property

(HG)*=G*H*

The proof should follow from assuming H is hermitian and applying that property to (H*H)*.

The basic way to solve the second part is to let [math]\lambda[/math] be an eigenvalue of [math]H[/math] and then evaluate [math]H*H \lambda [/math] using that the eigenvalues of H* are the complex conjugates of the eigenvalues of H
>>8600014
>That pic
Obvious bit of banter about a game that is already so shit. 4chan is so easily triggered.

>>8600014

I've actually only recently become allergic to tree nuts, but I seriously cannot stand the taste of some vegetables. Brussels sprouts, celery, etc.

I just don't like them.

>>8600038
>let λλ be an eigenvalue of HH and then evaluate H∗HλH∗Hλ using that the eigenvalues of H* are the complex conjugates of the eigenvalues of H
Ugh that came out horrid. Let me redo that.

The basic way to solve the second part is to let λ be an eigenvalue of H and then evaluate H*H λ using that eigenvalues of H* are the complex conjugates of the eigenvalues of H.

To anyone good with the brain, how severe would a few glasses of wine on one night at about age 9-10, and then about 10 drinks total spread across all of high school with no more than one drink in a single 24 hour period affect one's overall iq?
Sorry if this isn't the board for it but I've been curious for a while and finally just going to give it a go here for an answer.

Is there a symbol for science in general?

How can I git gud at math? Or rather, how can I recognize patterns faster? It seems like a lot of the other students in my class are a step or two ahead of me when it comes to logically going through the motions of a problem.

>>8600128
>How can I git gud at math?
What are your goals specifically? What class are you taking?

Just do a lot of problems and you'll improve. working through a more advanced text on the subject you're taking in parallel with the course helps sometimes. If I had more info I could make specific recommendations.

>how can I recognize patterns faster?
I'm just kind of assuming you've just started to do proofs and want to get better at them. After you've done hundreds or thousands of proof problems, you know common tricks and paths and setups to finding a proof that works. It's kind of shitty but really the only way to get better at this stuff is hard work.

In general, pattern recognition is a component of what's called "fluid intelligence," and that doesn't change very much unless you're a fairly young child or had head trauma or meningitis or something.

I'm not saying that math is easy, but you don't need to be a genius to do well in undergraduate/first year graduate math so don't get discouraged by that.

Can someone post a neat infographic of the levels of math, and extra points if books are included for each topic.

Like what I should know as an undergrad, what I should be reading as a grad student, what I should know after graduating with a math phd..


extra bonus points for /sci/s autistic standards (as in, real analysis being high school math - which, admittedly, maybe it should be)

>>8600070
8===D~

>>8594330
I feel like I would but it would take twice as long

>>8599428
What do you mean by "in 3d"? You want to find f(t)=<0,0,0>, or f(x,y,z)=0, or f(x,y,z)=<0,0,0>?

Either way, you can use the same basic idea. The main problems are that for the R^3->R case the solution tends to be a surface rather than a point, while for R->R^3 there generally isn't a root, only a least distance. R^3->R^3 maps points to points so there's usually some <x,y,z> s.t. f(x,y,z)=<0,0,0>.

>>8591198
college is fucking stupid guys

>>8600347
you more or less need it if you want a good normie job

http://www.realclearscience.com/quick_and_clear_science/2017/01/12/scientists_use_light_to_turn_mice_into_predatory_killers.html

How long until state-enforced brain implants and proxy wars between jewish elites?

>>8598160
You here. Yes I can.

>>8600468
>How long until state-enforced brain implants and proxy wars between jewish elites?


I just need you to let me stuff you back into the womb, do some genetic modifications, open up your skull, and shine some lasers around your brain.

Nothing major. I am glad you are being so understanding of your Jewish overlords.

>>8591198
Stupid question:
How do I find the basis of R^2?

Can anybody help me out here >>8599561 with a statistical mechanics problem?

Is there a program that "translates" mathematics symbols i dont understand in a ebook file?

>>8591688
your chicken looks like an ugly duck.

>>8599543
how many redpills have you shoved up your butt?

>>8591688
>>8594517
yeah that solution looks wrong

>>8600662
There isn't just one?

If the centrifugal force is a fictitious force acting only within a non-inertial frame, does that mean that if I'm pushed outwards in a moving carousel, if it suddenly disappeared the only force acting upon me would be the one tangent to the radius?

>>8600662
there are many bases of R^2

pretty much any two linearly independent points

orthogonal and in particular orthonormal bases are easier to work with

>>8600757
trying to translate your post
> If I was going in circles on a carousel and the carousel suddenly disappeared would I go in a straight line tangent to the radius?
yes, neglecting gravity, see slings

>>8596559
that is just a notation of the touble (a,bi) a, b being real i being imaginary written as a+b so you can do calculation with it the easy way and not have to think in tuples all the time

>>8600662
There's one canonical basis in (01) and (10), there are infinite bases formed any two vector whose rank is 2 , for example {(12),(21)} is a base

Waiting for someone to confirm

>>8600763
>>8600800
You are correct but how do I prove it's a base?

>>8600808
Take any group of vectors, put them in a matrix form, simplify it to a reduced echelon form (Gaussian elimination), and see the rank. If rank<n where n is the dimension of the vector space (2 in this case), then it's not its basis

>>8600808
i think you will have been given a definition for a basis

something like they are all linearly independant and they span the space

you will probably have been given a definition for span, or at least how to find it, then link it back to what R^2 is

Why does the white noise on AM radio get louder if you direct the antenna toward a metallic object?

>>8600770
Thanks

File: why.png (16KB, 797x596px) Image search: [Google]

16KB, 797x596px

Why is the answer to this E and not D?

I got that f(x)=G(2x)-G(4), where G(t) is the antiderivative of g(t), where g(t) is just the function inside the integral.

As such, f'(x)=g(2x)=sqrt[4x^2-2x]

So, f'(2)=sqrt[12].

Why is it actually 2sqrt[12]?

File: equatorialwisps.gif (628KB, 500x240px) Image search: [Google]

628KB, 500x240px

Made a thread but no one is bothering so I might as well give it a try here.

>I have 3 questions,
1. are the jets visible? besides emitting gamma rays and x-rays, how would they look like in the visible spectrum?
2. how would the powerful magnetic field affect the appearance of plasma around the start, or how would it affect an accretion disc around it?
3. how close could you get until the radiation kills you?

Am an artist and need a clear cut answer. pls help ;c

>>8601136
On a related note, why does sin((x+1)/x^2) not have a vertical asymptote at x=0? Is it just that vertical asymptotes only occur where the denominators of rational functions equal 0?

I'm aware of how this function looks when graphed, etc. Aware that the graph basically goes insane as you approach x=0, and then ceases to exist exactly at x=0. I guess just confused as to why the general rule regarding vertical asymptotes fails to work here.

>>8601144
oh, and the object i was talking about is a neutron star. i stupidly forgot to mention that.

>>8601136
I'm an idiot. f'(x)=2g(2x). Via chain rule.

Disregard my stupid question.

>>8601136
Apply the chain rule on G(2x).

>>8601147
Because [math]\lim_{x\rightarrow \infty}\sin(x)[/math] doesn't exist. One more thing, [math]\lim_{x\rightarrow 0}\sin\left(\frac{x+1}{x^2}\right) = \lim_{x\rightarrow \infty}\sin\left(\frac{\frac{1}{x}+1}{\frac{1}{x^2}}\right) = \lim_{x\rightarrow \infty}\sin\left(x^2\left(\frac{1}{x}+1\right)\right) = \lim_{x \rightarrow \infty}\sin(x+x^2).[/math] Basically, you're investigating what happens to [math]\sin(x)[/math] as [math]x[/math] approaches [math]\infty,[/math] but because you're working with a periodic function this just doesn't work.

https://www.youtube.com/watch?v=Bg1OvnLACts
what exactly is wrong with this

>>8601397
https://plus.google.com/wm/1/+enlongchiou/posts/bxtVxu8gX2N

it's supposed to be a proof of the riemann hypothesis?

https://www.youtube.com/watch?v=CBg-QQfvatE

>tfw dissected two Möbius strips of opposite chirality to get those intertwined hearts
>tfw she still said no
why can't i be cool just like the guys on youtube ;_;

>>8601568
difference between you and the cool guys is

you try 1 girl -> fail -> give up
they try 100 girl -> faill 99 (but never mention them) -> get 1 -> you see where this is going

>>8601621
this

>>8596521
Hey..

I helped a lot of Anons out ITT how about someone returns the favor..

What calculation would I use to figure out the odds of rolling at least two sixes on a given number of dice? I've googled a bit and everyone stops at combos and factorials.

>>8602086
if you have n dice
probability of getting at least two sixes
= 1 - (probablity of getting no sixes) - (probability of getting one six)
= 1 - (5/6)^n-(1/6)*(5/6)^(n-1)
= 1- (5/6)^(n-1)

>>8602113
Much appreciated, anon.

>>8599157
Depends on the class. Some professors will ask questions about magnetic fields that produce a torque upon an object, but in my experience, most stick with basic linear motion.

File: Screen Shot 2017-01-14 at 5.36.47 PM.png (63KB, 578x648px) Image search: [Google]

63KB, 578x648px

absolutely retarded question but is this a good symbol for particle physics?

>6 points for the six color charges and flavor charges
>made of an up and a down arrow representing [iso]spin states
>∓ in the middle for electric charges (with the negative preference)

In 3D, how do I calculate a velocity vector from a given rotation vector?

What is this symbol that looks like an `O` with a line through it.

https://wikimedia.org/api/rest_v1/media/math/render/svg/a23b704767638870ff6cdf592df0164f042c6c9b

File: 1.jpg (4MB, 2063x2853px) Image search: [Google]

4MB, 2063x2853px

Hey guys is this correct?
T-t-thanks.

>>8602303
depends on what direction you'e looking from. If Z is facing out of the graph and phi is towards positive Z then

X=cos(theta)sin(phi)
Y=sin(theta)sin(phi)
Z=cos(phi)

>>8602372
that's phi, usually used to either note a second angle after theta when used as a variable, or the golden ratio when used as a constant

>>8602381
And I realized that I forgot to add units to v at the end.

>>8602303
my mistake, that would be

X=r*cos(theta)sin(phi)
Y=r*sin(theta)sin(phi)
Z=r*cos(phi)

In set theory, what is a word?
The explanation I got was that it's a sequence of elements of arbitrary length that includes ε (which I don't even know what is either).
It then goes on to use words in the Kleene Star and I have no fucking clue what they do or how they're meant to be used.

>>8602447
the kleene star operator works like this

a* = {e, a, aa, aaa, aaaa, ...}
(ab)* = {e, ab, abab, ababab, ...}

in group theory a word is an element composed entirely of elements of a set and their inverses

in cs, a word is a string or substring composed entirely out of letters and digits with no whitespace, punctuation or other special characters

>>8602274
>jew star
no

File: 1483859527242.jpg (21KB, 400x400px) Image search: [Google]

21KB, 400x400px

I'm reading and wtaching math lecture but I feel like I'm learning way too slow. I feel like I learned way faster way back in school.

How can I speed up the learning process in STEM related subjects? Any tips & ideas?

>>8602743
when will the antisemitism meme die?

File: 1.png (9KB, 250x250px) Image search: [Google]

9KB, 250x250px

how about this as a symbol?

three lobes for the electronuclear forces and the center for gravity

>>8602381
B-b-bump

>>8603285
congrats you posted derivatives and you need someone to check over that shit please just spend a minute of your own time to look over it instead of posting it on an anonymous burmese anime forum

>>8603409
I think they are right, but I'm autistic and worried they are wrong, even though I've checked them and they are right. Hence I want to have someone else check so I can't stop worrying.

>>8603421
get some confidence man, they are right, just practice, do more of them, especially those with answer keys, or just plug them into an online derivative calculator. they're right btw

>>8603432
wait i said they're right twice maybe I'm the autist

what is the pw now for joelixny?

>>8603439
Kek. I also posted just in case my presentation could have used to tips.

>>8603432
And thanks man.

>>8602842
>illuminati eye
nah just playing with you, this one's better

>>8603421
you can use wolfram mathematica to check your derivations and visualize things

is the converse of lagranges theorem true?

for a group of order N, is there a subgroup for each factor of N?

i feel like it's the case but i can't prove it

>>8603810
from wiki

Existence of subgroups of given order[edit]
Lagrange's theorem raises the converse question as to whether every divisor of the order of a group is the order of some subgroup. This does not hold in general: given a finite group G and a divisor d of |G|, there does not necessarily exist a subgroup of G with order d. The smallest example is the alternating group G = A4, which has 12 elements but no subgroup of order 6. A CLT group is a finite group with the property that for every divisor of the order of the group, there is a subgroup of that order. It is known that a CLT group must be solvable and that every supersolvable group is a CLT group: however there exist solvable groups that are not CLT (for example A4, the alternating group of degree 4) and CLT groups that are not supersolvable (for example S4, the symmetric group of degree 4).
There are partial converses to Lagrange's theorem. For general groups, Cauchy's theorem guarantees the existence of an element, and hence of a cyclic subgroup, of order any prime dividing the group order; Sylow's theorem extends this to the existence of a subgroup of order equal to the maximal power of any prime dividing the group order. For solvable groups, Hall's theorems assert the existence of a subgroup of order equal to any unitary divisor of the group order (that is, a divisor coprime to its cofactor).

File: Retard2.jpg (2MB, 2031x2511px) Image search: [Google]

2MB, 2031x2511px

>>8602381

Guys can you help with pic related? It's related to the post I've cited above. Thanks, I-I-I'm retarded.

File: functional groups.jpg (137KB, 800x566px) Image search: [Google]

137KB, 800x566px

Quick chem question: ALL achiral diastereomers are meso compounds correct?

>>8603841
you wrote
> x=-1 or x=3
instead of
> t=-1 or t=3
Otherwise, it's correct

>>8603841
You're not dumb, you just lack self-confidence.

>>8591198
*sigh*

My name is Simon.

You are the only one still asking the right question. But you have called it a stupid question, which is correct. You have said it does not deserve it's own thread. Which is correct.

You have presented a sith lord. Which is correct.

Hello. My name is Simon.

What's yours?

>>8591198
I swear to god Howie, if this is you, I am so going to kick you in the balls.

Hello. My name is Simon.

>>8603968
Howie. IF this is you. You don't get to decide when. I have to enjoy the message you are sending me, but I have to reject it.

Otherwise convergence will always be feared, because they believe the golden ratio does not apply to everything.

But... thank you for keeping me company. And thank you for showing me something beautiful.

I am one with the force, and the force is with me.

Hello. My name is Simon.

>>8591198
Oh, I see. That's what mom sent me. The religion of c'düdles.

*sigh* I'm really going to enjoy your visit Howie.

>>8596521
>>8601917
someone?

>>8604001
Hello. I am someone. My name is Simon.

You referenced prior posts and now wish to repeat their message.

What assistance should I render?

>>8603924
>>8603924
Oh crap, didn't realize I changed the variable. I was tired when I did this and always used to writing x when solving quadratics.
So the explanation as to what occurs to the displacement of the object just before and after t=3 is correct?
Thanks guys.

>>8604009
How about not being a dick Simon? Is that an service that you provide?

>>8600877
Because the way an antenna works is by detecting fast switching voltages in open circuit. If you put both ends of this circuit close to a metal surface, you are basically creating a close circuit with two capacitors. Since the input of this circuit is sinusoidal with a high frequency, you're basically just connection the wires (obvious huge simplification) which means you can't detect the signal .The closer this distance become the more this is true.

Again, huge simplification, but might help with some basic intuition.

If I post assignment questions and my workings here, is there anyway my universities cheating detection software will find it?

>>8604292
possibly, but pretty unlikely, and you'd be the original author of your workings so it's not plagiarism for you, and it's usually allowed to get help with assignments

>>8604315
The assignment working are post here are rough working, the work I actually submit is written on different paper with a pen. So I hope that reduces the chances.

File: pfh.png (330KB, 742x835px) Image search: [Google]

330KB, 742x835px

>>8596818
>emails me today asking if i'm still alive
kek

This is a solar cell.

1) What is the function of each layer? In particularly PEDOT:PSS I'm confused by.

2) You're never actually adding a voltage source to a solar cell, right? So is this just a weird way of saying the hypothetical (-) side will negative and the (+) side positive?

File: 85465465.png (18KB, 540x439px) Image search: [Google]

18KB, 540x439px

>>8604489
derp forgot picture

>>8602496
I'm not sure I get it.
Do the elements of a sequence/pair/tuple whatever have anything to do with the elements of a set?

File: test1.jpg (71KB, 821x525px) Image search: [Google]

71KB, 821x525px

>>8603900
nope

pic related

>>8596818
be honest with her and answer her emails, imagine yourself how annoying it would be if someone ignored your emails, tell her you've been very busy but you're working on it

What do universities look at in transfer applications? I have a 3.75 and I'm trying to transfer to Georgia Tech in about a year, so I have some time to build some extracurricular stuff, etc.

>>8604501
Please elaborate to a brainlet.
Left molecule is meso and right molecules are
mirror-images and non-superposable thus enantiomers.