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Math essay by Doris Chabblesadge - Fri, 17 Oct 2014 15:57:47 EST ID:GWtHalR/ No.14416 Ignore Report Reply Quick Reply
File: 1413575867752.jpg -(496136B / 484.51KB, 768x4096) Thumbnail displayed, click image for full size. 496136
I'm taking a forced module that requires you to write an essay and do a presentation on a topic in math that isn't normally covered in the standard syllabus. For the essay you basically need to rewrite a chapter of a text book including theorems, proofs, examples, diagrams etc.

Could anyone recommend some interesting topics? Some topics that people have done in the past are:

-rubik's cubes and group theory
-p-adic numbers
-set theory and axiom of choice
-hilbert spaces
-algebraic curves
-queuing systems

I'm in my second year so it can't be a topic that's too difficult to understand.
3 posts omitted. Click Reply to view.
Shit Gabblemug - Sat, 25 Oct 2014 15:55:16 EST ID:GWtHalR/ No.14440 Ignore Report Quick Reply
Thank you for this
Jarvis Blimmerhall - Tue, 28 Oct 2014 18:44:58 EST ID:1xiHvl+b No.14454 Ignore Report Quick Reply
"In one sense, there are twice as many numbers between 0 and 2 as there are between 0 and 1 (because 0 to 2 is twice as "long" as 0 to 1); but in another sense there are exactly the same number of numbers between 0 and 2 as there are between 0 and 1.

>[Undefined, grammatical filler] there are twice as many numbers between 0 and 2 as there are between 0 and 1
>[Undefined, grammatical filler] there are exactly the same number of numbers between 0 and 2 as there are between 0 and 1.

"This is beginning to approach the level of comfort you need with the quirks of infinite collections of numbers to understand the Banach-Tarski theorem. If you're not quite comfortable with this so far, please go back and reread before continuing on. "

you shouldn't have
Cornelius Blackwater - Tue, 28 Oct 2014 21:04:48 EST ID:EsiytcUg No.14455 Ignore Report Quick Reply
1414544688473.gif -(9127B / 8.91KB, 410x276) Thumbnail displayed, click image for full size.
Check out Ramsey theory, it's about inveitable structures, pretty juicy stuff philosophically. "Total disorder is impossible". It's one of those lovely areas that have problems that are (relatively, given a certain audience) simple to formulate but difficult to solve.

"Suppose aliens invade the earth and threaten to obliterate it in a year's time unless human beings can find the Ramsey number for red five and blue five. We could marshal the world's best minds and fastest computers, and within a year we could probably calculate the value. If the aliens demanded the Ramsey number for red six and blue six, however, we would have no choice but to launch a preemptive attack." - Erdos
Edward Wodgebanks - Tue, 18 Nov 2014 03:09:28 EST ID:pAQz9OgX No.14492 Ignore Report Quick Reply
ooo ooo ooo non-standard analysis
Lillian Demmlepodge - Fri, 21 Nov 2014 06:56:16 EST ID:GWtHalR/ No.14493 Ignore Report Quick Reply
Good idea but unfortunately we've already covered it in a combinatorics module. My lecturer used that quote too :)

I'll look into it. Good topic too as I could present the criticisms against it too.

sound synthesis by Jarvis Huddlefuck - Mon, 17 Nov 2014 08:55:10 EST ID:RJugJy5x No.14488 Ignore Report Reply Quick Reply
File: 1416232510655.jpg -(44823B / 43.77KB, 500x500) Thumbnail displayed, click image for full size. 44823
So, I put this in music and production seing as its sound synthesis but the mods locked the thread so will try here..

can ANYONE help with these questions? any input appreciated.
Jarvis Fuckletire - Mon, 17 Nov 2014 18:56:03 EST ID:d/+G3sr/ No.14489 Ignore Report Quick Reply
frequency modulation

Wc = carrier frequency; i = modulation index; Wm = modulation frequency
Faggy Pinkinhick - Mon, 17 Nov 2014 22:32:49 EST ID:sVDeU0lu No.14490 Ignore Report Quick Reply
I don't know what's up with that mod, seemed like it belonged in /m/. It's called music & production board after all.
Charles Geblingworth - Mon, 17 Nov 2014 23:01:06 EST ID:bccTK08l No.14491 Ignore Report Quick Reply

thankyou friend, it is appreciated

Is this a problem? by Clara Chisslesore - Sun, 19 Oct 2014 21:54:03 EST ID:IJ85y6zt No.14423 Ignore Report Reply Quick Reply
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Is it a problem that set theory is based on mathematical logic, whereas mathematical logic is based on set theory? If so, why?
4 posts and 1 images omitted. Click Reply to view.
Polly Dambleville - Mon, 27 Oct 2014 20:56:01 EST ID:jEbtLayo No.14452 Ignore Report Quick Reply
I think he's referring to the fact that in order to define truth in first order logic you have to use structures, which are sets equipped with functions and relations. You need to know how these things work in order to set up FOL but in order to formalize sets you need FOL.
Edward Cuzzlehall - Sat, 01 Nov 2014 13:25:09 EST ID:Dk8yywxc No.14461 Ignore Report Quick Reply

A first order theory doesn't have a truth function. A first order theory has axioms, rules of deduction, and a language to express it in. There are no sets, only names that are being manipulated using rules, and the resulting theorems. Of course you can talk about a model (structure) for a first order logic where you can have sets and a truth function but the theory itself is more fundamental and acts as a building block.

It's confusing because when you come up with a theory, you intuitively have in mind what the theory means, i/e you already have a structure in mind. So if I'm talking about the theory of natural numbers then 1=1 is valid (true in every structure), but when you separate the theory from the structure 1=1 is only a theorem, there is no notion of true or false. In a theory you only have the starting place and the theorems that result from it. 1=1 here isn't a statement about numbers, it is just symbols that are neither true or false, we just got it from manipulating some symbols that we started with.

I should mention that there is already the idea of a functions and predicates within the language, but there is formally not a truth function until you have a model. You do, however, need some set theoretic notions to begin talking about structures and models as you mentioned. But it is really basic stuff that doesn't seem to be problematic in this case, questions like "what is a set". My main point though is that a first order theory doesn't need set theory. Set theory needs the first order theory, while structures and models need (basic) set theory.
Phoebe Turveyspear - Tue, 04 Nov 2014 02:03:56 EST ID:jEbtLayo No.14465 Ignore Report Quick Reply
If you take deductive systems as your primitive constructions then you can construct set theory without ever referring to sets. The only problem here is that you can't have any notion of soundness or completeness until you define some notion of truth. I see what you're saying though, usually it's taught by defining truth first and then talking about deductive systems which never quite sat well with me since you had to use sets/functions/relations and all of that stuff without ever formally defining them.
Hamilton Buddlemack - Wed, 05 Nov 2014 12:24:47 EST ID:Dk8yywxc No.14466 Ignore Report Quick Reply

Completeness can be interpreted as meaning for every formula A, you either have A or -A as a theorem, i/e every formula A is decidable. You don't quite need truth to do that. You're right about soundness though, it refers to the validity of a formula, which is a statement about models essentially. Can't have models without sets.
Molly Goodgold - Sat, 08 Nov 2014 21:47:13 EST ID:jEbtLayo No.14471 Ignore Report Quick Reply
I meant completeness in the sense that every true statement in first order logic is deducible. http://en.wikipedia.org/wiki/G%C3%B6del%27s_completeness_theorem
They really need to have another name for this.

How to Break Even + Profit on boxed software? by Yaranaika - Tue, 12 Aug 2014 14:20:06 EST ID:8ADnuosf No.14279 Ignore Report Reply Quick Reply
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Ok, say a piece of software in a boxed copy is $150 solid.

To break even would be to make $150 back on every copy correct?

To profit slightly without being accused of scalping would be maybe $50 on the original price? (I'm selling these at an anime convention, so I need to pay off my table and eat too...)

I've sold goods at 200% Markup last year but these are more physical and mystically rare items like certain foods, unlocked import phones from Japan...etc
Angus Brirringkadge - Thu, 06 Nov 2014 14:24:24 EST ID:REpT3xaI No.14467 Ignore Report Quick Reply
1) How much money do you need to make to cover expenses and your investment? 2) How many units do you expect to sell?
Cut the second number into a third and divide that into the first number. (#1)/(#2/3)

That's your reasonable markup price

Discrete Math and Counting by Martin Chashway - Tue, 21 Oct 2014 01:39:18 EST ID:vbQtHDF1 No.14432 Ignore Report Reply Quick Reply
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Hi /math/, I've got a question regarding counting in Discrete Mathematics. The textbook I have, "Discrete Mathematics With Ducks," is truly garbage and not helpful at all when it comes to... anything. http://www.amazon.com/product-reviews/1466504994/ref=acr_dpx_hist_1?ie=UTF8&filterBy=addOneStar&showViewpoints=0

The question I'm on asks:
How many positive integers solutions are there to the equation y1 + y2 + y3 + y4 + y5 + y6 = 13?

I need some help with this. After break I'm a bit lost. This is under the section of Combinatorial problems, and we've been using the Principle of Inclusion and Exclusion as well as this "stars and bars" technique (I'm not sure if anyone is familiar with this, it might just be my god-awful textbook). So ideally the problem could be solved that way. Thanks.
Esther Sengerford - Tue, 21 Oct 2014 10:52:03 EST ID:Dk8yywxc No.14433 Ignore Report Quick Reply

I don't know about stars and bars but here is how I would think about this.

This problem is like trying to put 13 balls into 6 boxes with at least one ball in each box. Put a ball in each box, so there are 13-6= 7 balls remaining. You can distribute the remaining 7 in C(7+6-1,7)=C(12,7)=792 different ways to do it. The reason there is a -1 is because we don't want 0 to be included.
Basil Gesslepark - Fri, 31 Oct 2014 19:17:48 EST ID:dJKFjM4J No.14460 Ignore Report Quick Reply
Stars and bars? Just imagine a whole bunch of numbered blocks, 1 .. N. You wrote down 5 plus signs. We're going to remove 5 blocks from the N. This will allow removing 5 consecutive from the left, that's okay for now. The spacing between the blocks indicates the grouping of the integers (so an island of 5 blocks: y_k = 5). The only trouble is you specified positive integers, so we should eliminate all the solutions containing 0.

First, how big is N? N should allow for 13 blocks after removing 5, so N = 18.

So the answer is less than (18 5).

Instead of adding up to 13, we could just distribute a 1 to each y_k and add up to 13 - 6 = 7. So (7 5) would represent all the ways to introduce splits in the remaining 7 numbered blocks to distribute them uniquely to y1..y6.

(7 5) = 42, so the answer is 42? It's either 792 or 42, who knows.

Refreshing math knowledge. by Ian Tootson - Wed, 29 Oct 2014 11:54:18 EST ID:GCILLCAz No.14456 Ignore Report Reply Quick Reply
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I'm a undergraduate math major who has been out of college for about 2 years. I want to go back to uni but I am extremely rust on my higher level math skills. What tools or resources could I use to revive my mathematics knowledge? This is where my poor note taking has taken its toll.
Should I just use math GRE subject test practice books or do you know of any thing that will help. I am not looking to relearn like kahn academy just practice tests for calculus, linear algebra, multuvariate, and complex.
Thomas Bepperkit - Thu, 30 Oct 2014 11:54:13 EST ID:Dk8yywxc No.14458 Ignore Report Quick Reply

If you don't remember it and aren't taking classes yet, buy some positively reviewed textbooks. Work through them and do some exercises too. Don't forget to do a couple of exercises!

A little bit of google searching should find you some books that people generally regard as good. Don't worry if you work through them slowly, just keep at it every day.
Alice Bardwill - Fri, 31 Oct 2014 12:07:00 EST ID:Ov5dnuCH No.14459 Ignore Report Quick Reply
For calculus just pirate a copy of the Stewart textbook and go through it. It's your standard plug n chug textbook and a huge number of universities use it so it'll put you in good stead for when you're finally back. If you get stuck you can always supplement with the internet. It goes all the way up to multivariable calc, vector calc etc.

Same for linear algebra really. The book we use is "Linear Algebra - A Modern Introduction". Again it can be pirated online.

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
File: 1389332443035.jpg -(34265B / 33.46KB, 400x329) Thumbnail displayed, click image for full size. 34265
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.

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