Leave these fields empty (spam trap):
Name
You can leave this blank to post anonymously, or you can create a Tripcode by using the format Name#Password
Subject
Comment
[i]Italic Text[/i]
[b]Bold Text[/b]
[spoiler]Spoiler Text[/spoiler]
>Highlight/Quote Text
[pre]Preformatted & Monospace Text[/pre]
[super]Superset Text[/super]
[sub]Subset Text[/sub]
1. Numbered lists become ordered lists
* Bulleted lists become unordered lists
File

Sandwich


420chan is Getting Overhauled - Changelog/Bug Report/Request Thread (Updated July 26)

What kind of graph is this?

View Thread Reply
- Mon, 01 Dec 2014 06:14:44 EST pok0PfIZ No.14500
File: 1417432484691.jpg -(205525B / 200.71KB, 850x850) Thumbnail displayed, click image for full size. What kind of graph is this?
Weird question I know, but I'm really high and this thing is reading like a fucking fractal

%Wasn't quite sure where to post this, apologies if I'm on the wrong board%
>>
Lydia Parringhall - Mon, 01 Dec 2014 12:22:59 EST L5NP4VLn No.14501 Reply
>>14500
It's a Venn diagram
Doesn't look very fractal really..

Clearly I need to review something...

View Thread Reply
- Wed, 26 Nov 2014 17:42:16 EST RzQObfiO No.14496
File: 1417041736839.png -(102378B / 99.98KB, 852x620) Thumbnail displayed, click image for full size. Clearly I need to review something...
Can someone explain this to me? It seems like I do not understand factoring at all.

I have no idea how x = 0, 3, and -2.

Thanks in advance.

Math essay

View Thread Reply
- Fri, 17 Oct 2014 15:57:47 EST GWtHalR/ No.14416
File: 1413575867752.jpg -(496136B / 484.51KB, 768x4096) Thumbnail displayed, click image for full size. Math essay
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
-cryptography
-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.
5 posts omitted. Click View Thread to read.
>>
Cornelius Blackwater - Tue, 28 Oct 2014 21:04:48 EST EsiytcUg No.14455 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 pAQz9OgX No.14492 Reply
ooo ooo ooo non-standard analysis
>>
Lillian Demmlepodge - Fri, 21 Nov 2014 06:56:16 EST GWtHalR/ No.14493 Reply
>>14455
Good idea but unfortunately we've already covered it in a combinatorics module. My lecturer used that quote too :)

>>14492
I'll look into it. Good topic too as I could present the criticisms against it too.

sound synthesis

View Thread Reply
- Mon, 17 Nov 2014 08:55:10 EST RJugJy5x No.14488
File: 1416232510655.jpg -(44823B / 43.77KB, 500x500) Thumbnail displayed, click image for full size. sound synthesis
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 d/+G3sr/ No.14489 Reply
frequency modulation

Wc = carrier frequency; i = modulation index; Wm = modulation frequency
>>
Faggy Pinkinhick - Mon, 17 Nov 2014 22:32:49 EST sVDeU0lu No.14490 Reply
>>14488
I don't know what's up with that mod, seemed like it belonged in /m/. It's called music & production board after all.

Is this a problem?

View Thread Reply
- Sun, 19 Oct 2014 21:54:03 EST IJ85y6zt No.14423
File: 1413770043603.jpg -(13898B / 13.57KB, 225x225) Thumbnail displayed, click image for full size. Is this a problem?
Is it a problem that set theory is based on mathematical logic, whereas mathematical logic is based on set theory? If so, why?
6 posts and 1 images omitted. Click View Thread to read.
>>
Phoebe Turveyspear - Tue, 04 Nov 2014 02:03:56 EST jEbtLayo No.14465 Reply
>>14461
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 Dk8yywxc No.14466 Reply
>>14465

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.

How to Break Even + Profit on boxed software?

View Thread Reply
- Tue, 12 Aug 2014 14:20:06 EST 8ADnuosf No.14279
File: 1407867606069.jpg -(84128B / 82.16KB, 381x543) Thumbnail displayed, click image for full size. How to Break Even + Profit on boxed software?
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 REpT3xaI No.14467 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

View Thread Reply
- Tue, 21 Oct 2014 01:39:18 EST vbQtHDF1 No.14432
File: 1413869958872.jpg -(23176B / 22.63KB, 250x346) Thumbnail displayed, click image for full size. Discrete Math and Counting
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 Dk8yywxc No.14433 Reply
>>14432

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 dJKFjM4J No.14460 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.

View Thread Reply
- Wed, 29 Oct 2014 11:54:18 EST GCILLCAz No.14456
File: 1414598058334.jpg -(49723B / 48.56KB, 1000x728) Thumbnail displayed, click image for full size. Refreshing math knowledge.
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 Dk8yywxc No.14458 Reply
>>14456

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 Ov5dnuCH No.14459 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?

View Thread Reply
- Sun, 26 Oct 2014 11:49:57 EST BH6DA7ss No.14443
File: 1414338597548.png -(800902B / 782.13KB, 1192x702) Thumbnail displayed, click image for full size. How do I prove this?
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 qABD7ibX No.14477 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

View Thread Reply
- Sat, 23 Aug 2014 17:06:36 EST 3fml9jmh No.14304
File: 1408827996393.jpg -(5682B / 5.55KB, 100x143) Thumbnail displayed, click image for full size. Calculus
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.
5 posts omitted. Click View Thread to read.

Is there anything to see here?

View Thread Reply
- Sun, 19 Oct 2014 12:29:00 EST FgPWXR9d No.14421
File: 1413736140638.jpg -(80374B / 78.49KB, 640x960) Thumbnail displayed, click image for full size. Is there anything to see here?
DICKS EVERYWHERE
>>
Alice Hodgebanks - Sun, 19 Oct 2014 18:04:04 EST uspvjvJI No.14422 Reply
no, it's just your imagination.
>>
Emma Pittshit - Tue, 21 Oct 2014 00:08:08 EST hu6SgEj9 No.14431 Reply
>>14421
well it's like the limit expression of e. I don't get why the (1+ is so important there.

Mathematical logic

View Thread Reply
- Sat, 18 Oct 2014 17:29:26 EST IJ85y6zt No.14418
File: 1413667766815.png -(106315B / 103.82KB, 320x287) Thumbnail displayed, click image for full size. Mathematical logic
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?
1 posts omitted. Click View Thread to read.
>>
Isabella Guddlelock - Sun, 19 Oct 2014 12:17:01 EST IJ85y6zt No.14420 Reply
>>14419
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 MTIV7/tU No.14426 Reply
>>14420
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 Dk8yywxc No.14428 Reply
>>14420

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

View Thread Reply
- Fri, 10 Jan 2014 00:40:43 EST G4lGyG09 No.13597
File: 1389332443035.jpg -(34265B / 33.46KB, 400x329) Thumbnail displayed, click image for full size. RNGs
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?
7 posts omitted. Click View Thread to read.
>>
Shitting Grimstock - Mon, 27 Jan 2014 13:46:27 EST pJYYYREs No.13639 Reply
1390848387982.png -(145633B / 142.22KB, 1920x1080) Thumbnail displayed, click image for full size.
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 K3z3WKaF No.14414 Reply
>>13597
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

View Thread Reply
- Tue, 07 Oct 2014 22:22:34 EST 9Czw1b2g No.14410
File: 1412734954064.gif -(2075656B / 1.98MB, 264x204) Thumbnail displayed, click image for full size. Trig sub
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 Gw2IN3ba No.14412 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 Gw2IN3ba No.14413 Reply
>>14412
Wait, scratch that. Just use x = u^2. The end result has inverse trigonometric form, but the substitution doesn't need to be trigonometric.

Report Post
Reason
Note
Please be descriptive with report notes,
this helps staff resolve issues quicker.