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1. Numbered lists become ordered lists
* Bulleted lists become unordered lists


How do I prove this? by Edward Lightford - Sun, 26 Oct 2014 11:49:57 EST ID:BH6DA7ss No.14443 Ignore Report Reply Quick Reply
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Can anybody help me with this problem?

let f(n)= sum (from i=2 to n) 1/(i ln(i)
Show that f(n) = Θ(ln(ln(n))
Edwin Brocklewell - Tue, 11 Nov 2014 13:41:05 EST ID:qABD7ibX No.14477 Ignore Report Quick Reply
∑1/(i*ln(i)) ≃ ∫dx/(x*ln(x)) = ∫1/x 1/ln(x) dx
Let u=ln(x), du=dx/x
∫ 1/u du = ln(u) = ln( ln(x) )

Calculus by cornelius - Sat, 23 Aug 2014 17:06:36 EST ID:3fml9jmh No.14304 Ignore Report Reply Quick Reply
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Anybody here recommend any books that are good introductions to calculus? I'm an idiot when it comes to anything beyond geometry and basic trig.
3 posts omitted. Click Reply to view.
Caroline Soffingkuck - Tue, 02 Sep 2014 23:01:27 EST ID:WLG9+3r6 No.14345 Ignore Report Quick Reply
> plus a semester of linear algebra.


if i had this years ago..
Archie Worthingfield - Sun, 07 Sep 2014 18:22:36 EST ID:xvgqavvT No.14353 Ignore Report Quick Reply
Sheldon Axler's Precalculus is the best out there I find. http://precalculus.axler.net/
He assumes you know/remember nothing about trig and goes from there, good introduction.

Khan Academy comes under fire from other mathematicians occasionally for presenting inaccurate info. Not a week goes by on HN where somebody doesn't call them out for shoddy lessons (which to their credit they clean up)
Phyllis Wullywill - Wed, 08 Oct 2014 00:08:44 EST ID:y2Fx3geS No.14411 Ignore Report Quick Reply
Any more like him besides khan?
Sidney Hammlegold - Thu, 23 Oct 2014 21:26:09 EST ID:IcAEoDAz No.14436 Ignore Report Quick Reply
Based Paul

Edwin Brocklewell - Tue, 11 Nov 2014 13:54:42 EST ID:qABD7ibX No.14479 Ignore Report Quick Reply

Is there anything to see here? by Graham Chacklestidging - Sun, 19 Oct 2014 12:29:00 EST ID:FgPWXR9d No.14421 Ignore Report Reply Quick Reply
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Alice Hodgebanks - Sun, 19 Oct 2014 18:04:04 EST ID:uspvjvJI No.14422 Ignore Report Quick Reply
no, it's just your imagination.
Emma Pittshit - Tue, 21 Oct 2014 00:08:08 EST ID:hu6SgEj9 No.14431 Ignore Report Quick Reply
well it's like the limit expression of e. I don't get why the (1+ is so important there.

Mathematical logic by Fanny Cicklefatch - Sat, 18 Oct 2014 17:29:26 EST ID:IJ85y6zt No.14418 Ignore Report Reply Quick Reply
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Let's say we disprove a set of hypotheses A. Each hypothesis is not as likely as each other to be disproved. How does one account for that? Does one use probabilistic logic to determine how likely each hypothesis is to get disproved? Or does one need to create a new type of logic entirely which gives a 'weight' to each hypothesis - how likely it is to get targeted and disproved?

For example ¬(A ∨ B) |- ¬e. How do we determine which set of hypothesis - A or B, is more likely to get targeted by disproval?
Jenny Cishfield - Sat, 18 Oct 2014 18:52:13 EST ID:Dk8yywxc No.14419 Ignore Report Quick Reply

I don't understand your notation, can you try rephrasing the question? Perhaps with an image?

Do you mean we're trying to prove some statements, and you're asking how likely it is each statement will be proved? If that is what you mean, it really depends on the statements themselves. Some statements are innately unprovable or you may not be able to prove it either way with the assumptions that you have made.
Isabella Guddlelock - Sun, 19 Oct 2014 12:17:01 EST ID:IJ85y6zt No.14420 Ignore Report Quick Reply
Let's say we have ¬(A ∨ B). How do we determine which is more likely to be false: A or B?
Samuel Mollersidge - Mon, 20 Oct 2014 08:43:18 EST ID:MTIV7/tU No.14426 Ignore Report Quick Reply
They are both as likely, since A v B is propositionally equivalent to B v A.
Or is there something I don't get here ?
Phoebe Mundlepin - Mon, 20 Oct 2014 11:03:05 EST ID:Dk8yywxc No.14428 Ignore Report Quick Reply

Lets try putting that into english. What you posted means "Not (A or B)", which could be rephrased as "neither A nor B". So if we have ¬(A ∨ B), we know that both A and B are 100% false.

Using a transformation rule called DeMorgans Law, we can pass the negation over the disjunction to obtain ¬A & ¬B.

If on the other hand the phrase was ¬(A&B), then we know either they are both false or only one of them is false. Using DeMorgans law yields

¬A ∨ ¬B

If you want to "really" find out which one is false, we need more information about A and B themselves.

RNGs by Caroline Crummleville - Fri, 10 Jan 2014 00:40:43 EST ID:G4lGyG09 No.13597 Ignore Report Reply Quick Reply
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Anyone know of a way to ACCURATELY predict dice rolls for RNGs? Specifically I am looking to predict dice rolls for Blood Bowl: Chaos Edition.

There used to be a program that did it but since then they made a patch and moved the algorithm and seeds to the sever side.

Anyone got ideas on how to do this?
5 posts omitted. Click Reply to view.
Samuel Secklesat - Wed, 22 Jan 2014 12:10:17 EST ID:G4lGyG09 No.13630 Ignore Report Quick Reply

It uses a mersenne twister with the seeds kept server side.
Jack Handermen - Fri, 24 Jan 2014 11:00:18 EST ID:sPd/0oB/ No.13631 Ignore Report Quick Reply
It's hard to do, really. The whole point of moving the seed to the server side is to make it almost impossible...

You could keep a sequence of random number (the original 32/64 bits sequence) fresh from the server, check how the seed is choosed and try to brute force the seed from here. For instance if the seed is a timestamp (it's common), pick several timestamp around the one you think is likely.
Even then you would need to keep track of how fast the RN are produced (is the server giving RN from the same seed to everyone?).

You need to decompile the server binaries to do that. If you don't have them, it's a lot harder.

You should ask this on /tinfoil/.
Ebenezer Movinghall - Mon, 27 Jan 2014 05:07:56 EST ID:DFb+IUXc No.13638 Ignore Report Quick Reply
Why not?
Shitting Grimstock - Mon, 27 Jan 2014 13:46:27 EST ID:pJYYYREs No.13639 Ignore Report Quick Reply
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There's nothing that some social engineering and espionage can't solve, Gentlemen.
Mangus von Vaginakowski !qrtrbnpccM - Wed, 08 Oct 2014 20:56:00 EST ID:K3z3WKaF No.14414 Ignore Report Quick Reply
Without access to the server or an exploit the DEVs fucked up on and left that allows you to do the [P]RNG, you're SOL.

Trig sub by Hedda Snodham - Tue, 07 Oct 2014 22:22:34 EST ID:9Czw1b2g No.14410 Ignore Report Reply Quick Reply
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Hey niggas i got this integral here: dx/((radx)(x+1))
some help setting up the trig sub would be greatly appreciated.
Cornelius Dartman - Wed, 08 Oct 2014 10:22:23 EST ID:Gw2IN3ba No.14412 Ignore Report Quick Reply
You need to perform two substitutions. First use x = sin^2(u). Then use v = sin(u).
Cornelius Dartman - Wed, 08 Oct 2014 10:38:17 EST ID:Gw2IN3ba No.14413 Ignore Report Quick Reply
Wait, scratch that. Just use x = u^2. The end result has inverse trigonometric form, but the substitution doesn't need to be trigonometric.

Relearning math by Wesley Blatherson - Wed, 10 Sep 2014 08:12:53 EST ID:D/oQWr2Y No.14356 Ignore Report Reply Quick Reply
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I've always been naturally bad at math, I failed algebra 2 twice in highschool because I just couldn't grasp the concepts fast enough. My sister who's a freshman in highschool asked me to help her with her homework, and I didn't know JACK SHIT.

I'm 20 and going to community college for a few courses while I work this upcoming spring, I don't plan to take math right away but is there some sort of program/books that will let me relearn math right from the beginning?
3 posts and 2 images omitted. Click Reply to view.
Hannah Penningcocke - Fri, 19 Sep 2014 11:15:59 EST ID:AJrEUkAQ No.14369 Ignore Report Quick Reply
I would love to help you with basic algebra/algebra 2!! I highly suggest taking math from the beginning, as you have quite a few semesters to make up to college-level courses if you're starting from the beginning. If you still won't do that, I suggest taking some time and learning some stuff on your own. http://khanacademy.com/ is an amazing resource; it's interactive, polished, and familiarizing yourself with stuff there will prepare you for doing mathematics on a computer, which you probably haven't done much since you haven't done math since high school.
Archie Goodman - Wed, 24 Sep 2014 13:12:32 EST ID:a8Tw8LvY No.14378 Ignore Report Quick Reply
>failed algebra 2 twice
I did 3 times, mostly because 2nd semester of algebra 2 is kinda bullshit. Now I'm in 3rd year engineering and I did Calc 3 a year ago
Rebecca Chorringfuck - Fri, 03 Oct 2014 11:45:44 EST ID:Z+iZvwQ7 No.14405 Ignore Report Quick Reply
Any site for physics? I'm taking capacitors and shit like that, electricity and magnetism. Need a good website for this stuff, preferably video. Youtube and khanacademy are insufficient.
Hedda Charringville - Fri, 03 Oct 2014 17:08:10 EST ID:V2nhYpJ2 No.14407 Ignore Report Quick Reply
MIT lectures
Might or might not be the correct section of the site, but if your answer cannot be found here you are either not looking close enough or undestanding it's in front of you.
Clara Crebblechodging - Fri, 03 Oct 2014 17:26:19 EST ID:xvgqavvT No.14408 Ignore Report Quick Reply
Re-learning math:

1) Lial's Basic College Math

This covers Kindergarten - Algebra. All the editions are the same so pirate/buy any of them.

2) Serge Lang's "Basic Mathematics" is great and will cover all you need to go into a rigorous theory based college math class. http://www.amazon.com/Basic-Mathematics-Serge-Lang/dp/0387967877/ref=sr_1_1?ie=UTF8&qid=1412284774&sr=8-1&keywords=serge+langs+basic+mathematics

There's also "No Bullshit Math" which does the same as Serge's book: http://minireference.com/ and Sheldon Axler's "Precalculus" which does the same.

I liked Serge's book. It's written by a Mathematician who doesn't hand hold or do anything else except teach you basic math from an advanced standpoint.. so you learn proper terms of everything and actually understand wtf is going on.

For Calculus I did MIT OpenCourseware 18.01 (Single) and 18.02 (Multi). There are no books, just lectures and assignments. After I did them I wanted to explore proofs more so did 18.014 and 18.024 (Both on the open courseware site). Basically all it consists of is doing a rigorous Calc book where you do a lot of proofs. I did them all in Scheme (because I was also trying to learn how to code). http://ocw.mit.edu/courses/mathematics/18-014-calculus-with-theory-fall-2010/ contains course notes by Munkres!! Awesome.
Comment too long. Click here to view the full text.

negative binomial help by Clara Fubblewill - Fri, 03 Oct 2014 15:03:16 EST ID:Aql4bjnf No.14406 Ignore Report Reply Quick Reply
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I'm trying to get the variance for hypergeometric discrete random variable without using the moment generating function and am having a lot of trouble.. I started with V(X)= E(X^2) - E(X)^2 and can get E(X)^2 but can't get E(X^2). Then someone suggested I try E(X(X+1)) but I don't understand how to do that.... Any help?

Clarification on velocity vector and acceleration by Fanny Nendlefetch - Mon, 29 Sep 2014 17:57:44 EST ID:dfurG/DB No.14392 Ignore Report Reply Quick Reply
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The problem is below; what my question is, is do I need to know t or what? If I don't, then what do I do and if I do need it, how do I find it?

At a certain moment, a particle moving along a path has a velocity v=<3,2,1> and a=<0,5,2>. Find T, N and the decomposition of a into tangential and normal components.

If I had a parametrized function for v I'd be good, but I don't because I don't know t...
Any help?
Fanny Nendlefetch - Mon, 29 Sep 2014 19:38:38 EST ID:dfurG/DB No.14393 Ignore Report Quick Reply
fac u op
Nell Foshfield - Wed, 01 Oct 2014 06:50:01 EST ID:Gw2IN3ba No.14402 Ignore Report Quick Reply
If by t you mean time, they don't provide that information and there is no way to deduce it. T here is kinetic energy and N is the normal force, yes? All you need to find T is the velocity and the mass (I assume the mass was provided earlier). Because the velocity must be tangential to the path at the point under consideration, you can use this to find the tangential and normal components of a. And the normal force is just the normal component of a scaled by m.
John Fendernidge - Wed, 01 Oct 2014 22:27:34 EST ID:kDYSaBHq No.14404 Ignore Report Quick Reply
To find tangential acceleration just project the a vector onto v

a_tan = a dot v/||v||

Then a_norm = a - a_tan

yay math

Help, what the fuck is P? by Fuck Donningdale - Thu, 25 Sep 2014 01:46:11 EST ID:aQ2ap22j No.14379 Ignore Report Reply Quick Reply
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How do I solve these?
Or what are the solutions?
3 posts omitted. Click Reply to view.
Lydia Pengerwone - Sun, 28 Sep 2014 17:55:22 EST ID:V2nhYpJ2 No.14390 Ignore Report Quick Reply
Actually because the function and boundaries are linear, the minima & maxima are at the intersections.
Lydia Pengerwone - Sun, 28 Sep 2014 17:58:00 EST ID:V2nhYpJ2 No.14391 Ignore Report Quick Reply
No wait, it can't be.
P = 10 - x - y;
f = { -10 < x < 10; -10 < y < 10 }
So what are the actual criteria for the minima & maxima being at the boundary and/or the intersections?
Martha Donkinherk - Mon, 29 Sep 2014 23:01:21 EST ID:umZ//85N No.14394 Ignore Report Quick Reply
1st one,
x-y <=4

use above two equations, solve for y
y<= 6 - x
y >= x - 4
y>= 0
since x <=5, and x-4 <= y, then the maximum of y is 1, thus we know
0<= y <= 1
at this point i think x is unbounded, meaning that P has no minima
but the maximum is x = 5 and y - 1 so Max P = 20
Martha Donkinherk - Tue, 30 Sep 2014 00:07:18 EST ID:umZ//85N No.14396 Ignore Report Quick Reply
never mind im retarded this isnt right
John Fendernidge - Wed, 01 Oct 2014 22:24:51 EST ID:kDYSaBHq No.14403 Ignore Report Quick Reply
lol you were right the first time. For your example the maximum is at one of the corners, x=y=-10

Linear Algebra and Matrices by Lillian Druddledone - Mon, 29 Sep 2014 23:56:43 EST ID:wV5uRW/L No.14395 Ignore Report Reply Quick Reply
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Hey guys, first post in /math/, hope you guys can help me out. Right now in Linear Algebra we're working with matrices (no surprises there) and I'm pretty confused on how to even begin solving this problem. We just recently learned about inverse matrices, transposed matrices, and matrix multiplication. Appreciate any guidance.
Barnaby Lighthood - Tue, 30 Sep 2014 02:06:20 EST ID:V2nhYpJ2 No.14397 Ignore Report Quick Reply
Consider, how would you solve
2x + 4 = 7x
The same holds here.
Lillian Druddledone - Tue, 30 Sep 2014 14:51:18 EST ID:wV5uRW/L No.14400 Ignore Report Quick Reply
Thanks for the tip, but I feel like matrices act differently. So I want to put the X's on the same side, but can I add/subtract the two matrices together?
Samuel Windledat - Tue, 30 Sep 2014 20:27:49 EST ID:V2nhYpJ2 No.14401 Ignore Report Quick Reply
IIRC that property is called distributivy and that should hold with matrix multiplication. Or I might be wrong.
driven !FTPgBqDDy. - Sat, 04 Oct 2014 23:07:55 EST ID:MSWrPT9p No.14409 Ignore Report Quick Reply
OP you need to group the X terms on one side, find the inverse of the matrix multiplying X (there is a formula for 2x2 matrix inverse), and then multiply both sides by the inverse yielding X = somematrix.

'cos a matrix multiplied by its inverse is the identity matrix.
and the identity matrix times X is just X, it's 1 in matrix terms.

What does this mesn? by Emma Bobberforth - Tue, 30 Sep 2014 10:01:26 EST ID:Vib06tOc No.14398 Ignore Report Reply Quick Reply
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Wesley Huffingbanks - Tue, 30 Sep 2014 10:34:08 EST ID:aO+d5dci No.14399 Ignore Report Quick Reply
first equation is called the gaussian integral, it's basically that the area under the curve y = exp(-x^2) is the square root of pi.

second equation is the fourier series of f(x), this is basically saying that you can write the function f as a infinite sum of sines and cosines.

last equation is the quadratic formula, it gives the solutions of ax^2+bx+c=0 , where a,b,c are real numbers.

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