Leave these fields empty (spam trap):
You can leave this blank to post anonymously, or you can create a Tripcode by using the format Name#Password
[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


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

1/0 = ∞

View Thread Reply
- Thu, 29 Jan 2015 21:34:01 EST iL1ckGCn No.14588
File: 1422585241954.jpg -(68549B / 66.94KB, 590x750) Thumbnail displayed, click image for full size. 1/0 =  ∞
1/ ∞ = 1 - .9(repeating) = 0

If 1/ ∞= 0 then 1/0 = ∞
9 posts omitted. Click View Thread to read.
Matilda Crillerwotch - Sat, 21 Mar 2015 11:07:23 EST Jz+dW0dw No.14660 Reply
>related rates aren't math

Wait till you start taking calculus?
Samuel Gebblestet - Tue, 24 Mar 2015 12:00:25 EST Dk8yywxc No.14664 Reply

This is not true in the real line. In the hyperreals, where arbitrarily large and small quantities are included unlike the "standard" reals, 1/0.000...1 with infinitely many zeroes is indeed infinity. However 1/0 is just undefined and there is nothing more to it than that.

In short, the formal system you're taught in calculus can't handle it but there are systems that can.


View Thread Reply
- Tue, 24 Mar 2015 05:18:08 EST nIRThw+j No.14662
File: 1427188688076.jpg -(42148B / 41.16KB, 721x303) Thumbnail displayed, click image for full size. hmmmm
Express 89.84 Mbps and 2.49 Mbps in bits per second (bps) using scientific notation.


View Thread Reply
- Wed, 18 Mar 2015 01:56:40 EST DYY7KYkl No.14645
File: 1426658200314.jpg -(132478B / 129.37KB, 698x332) Thumbnail displayed, click image for full size. probability
If there is a function that returns a random number from 1-7, why can't I add the result of this function 5 times to get a uniform distribution of 5 to 35?

rand5() + rand5() + rand5() + rand5() + rand5() != uniform [5,35]

wtf I can't wrap my mind around why this doesn't work!! I've been told you can't sample a random uniform distribution to create a new random distribution and something about the central limit theorem. Can I get an intuitive answer?
7 posts and 2 images omitted. Click View Thread to read.
Cuntfuck - Thu, 19 Mar 2015 16:07:14 EST xgdLZpNp No.14656 Reply
Because that's not how random works?
Priscilla Hezzlemore - Sat, 21 Mar 2015 06:14:50 EST qz3c7Bt+ No.14658 Reply
1426932890860.gif -(4378B / 4.28KB, 629x115) Thumbnail displayed, click image for full size.
You must use combinatorics.
Priscilla Hezzlemore - Sat, 21 Mar 2015 06:20:27 EST qz3c7Bt+ No.14659 Reply
1426933227860.gif -(1566B / 1.53KB, 331x49) Thumbnail displayed, click image for full size.
oops that last part was not up to /math/ standards


View Thread Reply
- Thu, 19 Mar 2015 15:26:51 EST lxw6acDK No.14654
File: 1426793211813.jpg -(205881B / 201.06KB, 1024x768) Thumbnail displayed, click image for full size. Beginnings
>3rd yr Winter Semester
Currently taking :
>Calc 3
>Abstract Algebra

I want to understand and design electronics but end goal is I Entrepreneurship

Course suggestions for my senior yr before I'm out in the wild?

Ability of other species to conduct mathematics

View Thread Reply
- Sun, 15 Mar 2015 04:05:09 EST M7BdweVS No.14637
File: 1426406709949.jpg -(652675B / 637.38KB, 1800x1200) Thumbnail displayed, click image for full size. Ability of other species to conduct mathematics
I would like to postulate the question of which if any animals are capable of math besides Homo sapiens?

Some notable contestants:

African Grey Parrot, estimated to have the cognition/IQ of a 4 year old child.
Octopus, possibly the smartest creatures without a bone structure
Chimpanzees, our 'closest' cousins known to fashion tools
Crows, with a surprising brain-body ratio in proportion to Chimpanzees
Elephants, demonstrating self-awareness
Gorillas, historically taught to learn and speak sign language
Dolphins, our marine-mammal navigation crew on /1701/

Do you believe any of these animals could learn to use math? To what degree? Do you believe another creature could be a serious contender?
2 posts omitted. Click View Thread to read.
Fanny Wittinghut - Mon, 16 Mar 2015 15:53:08 EST SpD/fp2u No.14641 Reply
>Crows, with a surprising brain-body ratio in proportion to Chimpanzees
That's your description? Come on, crows have demonstrated some mind-blowing cognitive abilities.

But yeah, like Lillian says, so far it's all repetition and parroting from my understanding. Wouldn't it be cool to make it your life legacy to be the one who successfully teaches a non-human to math?
Fanny Wittinghut - Mon, 16 Mar 2015 15:57:41 EST SpD/fp2u No.14643 Reply
Actually you didn't leave out octopus, apparently I am drunk

Help learning gcse maths

View Thread Reply
- Sat, 03 Jan 2015 10:45:28 EST NxPbw8hD No.14549
File: 1420299928533.jpg -(111066B / 108.46KB, 603x376) Thumbnail displayed, click image for full size. Help learning gcse maths
Im 25 and im back in college learning maths.The lesson is only one 2 hour lessons a week and to be honest I feel like ive learnt nothing there at all.Its hard and I just seem t learn better by my self.

My problem I have though is where the fuck should I start of,there is so much shit I dont know like I barely even know what a fuckin prime number is.

I only want a c but I need that so I can go onto an access course.

SO what should I do to learn maths (I dont like khan academy found a few other sites though)

Like when I say what should I do what subjects should I Start of learning first ?
IM going to take the whole of next week while im still of work to learn as much so I need a plan on what to start of learning first.
Alice Snodshit - Fri, 09 Jan 2015 07:33:19 EST ev+cRfEi No.14555 Reply
1420806799155.jpg -(15047B / 14.69KB, 460x348) Thumbnail displayed, click image for full size.
So at the moment Im trying to learn fractions but I keep on fucking up with baisc things like simplifying and converting ratios and the rest of it.

Im thinking I may need to go back a few steps as im not perfect with my time tables dont know all my prime numbers ect.
Wherre would you say I should start of with wht subjects ?

>btw Ive got to learn as muh as I can of thse by tuesday for a mock test im going to be doing


expand brackets

angles in polygons

>Where should I start off what subject ??
Hugh Collerfoot - Thu, 05 Feb 2015 22:24:09 EST Gj+82UIb No.14595 Reply
All you need is Basic Mathematics by Serge Lang. It covers everything, from the view of a professional mathematician explaining how the magic works. Torrents for it everywhere also can buy it used for cheap. Covers all of highschool and is a good precalc book.

After Basic Math get these short books:
How to Prove It: A Structured Approach
How to Solve it by Polya.

Now you are ready for any rigorous university level classes
Rebecca Cushforth - Sun, 15 Mar 2015 04:25:46 EST JDIWTmrz No.14638 Reply

Work through the following:

Algebra by Gelfand and Shen
Functions and Graphs by Gelfand, Glagoleva, and Shnol
The Method of Coordinates by Gelfand, Glagoleva, and Kirillov
Trigonometry by Gelfand and Saul
Kiselev's Geometry


View Thread Reply
- Thu, 26 Feb 2015 17:18:10 EST Yi4ytYm1 No.14616
File: 1424989090559.jpg -(25012B / 24.43KB, 344x475) Thumbnail displayed, click image for full size. Analysis
Due to circumstances I was unable to participate in my first analysis course. Now I have to take the next one (individually both take half a semester). I want to go through the important parts of the previous course, but while there is practice material, there is no material with solutions. I asked my professor about solutions to the homework excersizes, but he isn't giving them. Does anyone know of any, preferably free, practice material? The topics coverd is basically this book, plus some extra stuff on sets (boundaries/compactness) and integration.

I did find this:
But I'm not sure how trustworthy the site is.
6 posts omitted. Click View Thread to read.
Nigel Figgleputch - Wed, 04 Mar 2015 07:17:41 EST weDVNH8d No.14627 Reply
I did not merge with the math community and neither had i very splendid start. So i need to be very self-reliant for now.
The professor who teaches analysis uses Tao's book. I like it except the fact it doesn't have solutions. Rudin's book has them, so good reason to train my devotion haha.

But there is also group theory and syllabus we got doesn't have solutions either. Anyone a good introductory book they're fond of?
Nell Ceblingfoot - Mon, 09 Mar 2015 20:29:01 EST JDIWTmrz No.14632 Reply
Read Baby Rudin. All the exercises are online.

just sayin

View Thread Reply
- Thu, 05 Mar 2015 23:48:50 EST PmLosP1P No.14628
File: 1425617330260.gif -(195877B / 191.29KB, 360x235) Thumbnail displayed, click image for full size. just sayin
I like the idea of q-analogs but I think they're a little too advanced for selfstudy and that's all I've got at the moment.

I also like the idea of fractional calculus (same kind of realm in a way?) but that seems like something I could study on my own.
Eliza Seggledet - Sun, 08 Mar 2015 01:45:50 EST F9AJX/Os No.14629 Reply
i like your picture.

although i dont get why they used (x^2)/2 instead of just x^2.
Fanny Sacklested - Sun, 08 Mar 2015 06:04:20 EST nxCnniYW No.14630 Reply
because (x^2)/2 is the antiderivative of x, and 1 is the derivative. its from the wiki page on fractional calculus.

always messing up the basics

View Thread Reply
- Mon, 23 Feb 2015 22:03:13 EST zBSUDYOt No.14612
File: 1424746993952.png -(4013B / 3.92KB, 540x358) Thumbnail displayed, click image for full size. always messing up the basics
so anytime I see a problem like im about to write I always shit the bed and forget the basics with out further ado my nemesis so instead of simply giving me the answer Id rather like to have people interact with me as I try to preform this.
(2u^-5 * v^2
so for starts I need to distribute ^-2

(1/4u^10 * v^-4)
So if Im understanding this fraction within a fraction everything is going to switch between the numerator and the denominator except for 1/4u^10 because its not raised to a negative power thus.

64w^2 * 1/4u^10
then multiply the numerator


Does this look right sorry if Its hard to read Ill write up a jpg
2 posts and 1 images omitted. Click View Thread to read.
Jack Hammerfoot - Sat, 28 Feb 2015 03:01:48 EST e+7yrnP7 No.14619 Reply
The key to the top part of 17 is knowing that
a^2 - b^2 = (a + b)*(a - b)
The bottom part is trickier, but one of the terms needs to have a 2x
Jack Hammerfoot - Sat, 28 Feb 2015 03:02:52 EST e+7yrnP7 No.14620 Reply
I guess i should say, it's not 'knowing' it's observing the algebra. Splitting these equations up is mainly a trial and error sort of deal where the more practice you get the faster/better you are


View Thread Reply
- Thu, 26 Sep 2013 03:14:08 EST Mpud+AHb No.12970
File: 1380179648574.png -(22163B / 21.64KB, 1024x739) Thumbnail displayed, click image for full size. guides/tutorials
anybody have good simple tutorials/guides on using SAS and or LATEX?
6 posts and 1 images omitted. Click View Thread to read.
Walter Drendlekidging - Sat, 21 Feb 2015 13:38:57 EST Dk8yywxc No.14610 Reply

Sage math cloud is great. You can do latex and other languages, and gives you a preview as you type that you can access anywhere.
Nathaniel Sarringbire - Sun, 22 Feb 2015 23:00:38 EST yFfkLiLW No.14611 Reply
Seconding Sage. Maybe it's because I'm a noob mathematician, but I've never needed another CAS. Can't beat free!

unless matlab counts as cas

Different ways to prove that the square root of any prime number is irrational

View Thread Reply
- Wed, 17 Dec 2014 01:02:18 EST XuUSwld1 No.14534
File: 1418796138255.png -(1345218B / 1.28MB, 1920x816) Thumbnail displayed, click image for full size. Different ways to prove that the square root of any prime number is irrational
And I'm not satisfied with the indirect proof:
x^(1/2) = a/b | If 'x' is prime and both 'a' and 'b' are integers
x = (a^2) / (b^2)
(b^2) *x = a^2| Therefore 'a' is a factor of 'x' and...
(b^2) *x = (x^2)(c^2)
(b^2) =x(c^2)|.... 'b' is also a factor of 'x'
I don't think this is enough proof to go off of and say that 'x^(1/2)' is irrational, but I'm coming down off my coffee buzz right now and I wanna see what /math/ thinks while I brew the next pot.
1 posts omitted. Click View Thread to read.
Charles Murdford - Thu, 15 Jan 2015 19:56:16 EST h2IBC+4I No.14564 Reply
Little late. I won't type out all the details but a wonderful proof of this goes like:

Let p be prime, GCD (a,b)=1, and p=(a/b)^(2) b neq 0. So


Now consider the prime decomposition of a^(2). There has to be an even number of primes (a=p_(1)...p_(n) so aa=p_(1)...p_(n) which means there are 2n primes in the decomposition). Now look at the left side. A similar argument shows b^(2) has an even number of primes in it's prime decomposition, but p is also prime. So the left side of the equality has an odd number of primes in the prime decomposition and the right has an even. This contradicts the fund. theorem of arith. as the prime decomposition must be unique which means they have to have the same number of primes in their decompositions.
Charles Murdford - Thu, 15 Jan 2015 19:56:59 EST h2IBC+4I No.14565 Reply
made a mistake meant to say aa=p_(1)...p_(n)p_(1)...p_(n)

math question

View Thread Reply
- Thu, 22 Jan 2015 14:43:35 EST yDDqWeTL No.14571
File: 1421955815798.jpg -(9639B / 9.41KB, 240x240) Thumbnail displayed, click image for full size. math question
hi. for a calculus assignment i have i have completed all but this final question:

A stereo manufacturer determines that in order to sell x units of a new stereo, its price per unit must be p = 1000 − x. It also determines that the total cost of producing x units is given by C(x) = 3000 − 20x.
a. Find the total revenue equation, R(x).
b. Find the total profit equation, P(x).
c.How many units must the company produce and sell to maximize profit.
d. Find the max profit

not very familiar with finances in relation to functions and my prof never touched on it nor is it in my textbook! any input / solutions with explanations would be ideal.. thanks
1 posts omitted. Click View Thread to read.
Shitting Sullerchutch - Sat, 07 Feb 2015 16:03:40 EST cMHknuu4 No.14598 Reply

I' m a pretty big math newbie. But shouldn't you want to determine whether dP/dx = 0, is a minima or maxima?
Rebecca Bicklestock - Sat, 07 Feb 2015 16:31:37 EST tX1aaDR5 No.14599 Reply
Since your profit eq is of the form -ax^2 + bx -c, then we know that the parabola opens DOWN (just graph a generic -x^2 to see this). So finding the point at which the slope = 0 is akin to finding the max. You should write this reasoning as part of the answer
Rebecca Bicklestock - Sat, 07 Feb 2015 16:33:19 EST tX1aaDR5 No.14600 Reply
Actually, its probably faster to just show it's the max by picking a point to the left of it, and to the right. Showing a generic graph seems like a lot of work compared toj ust picking points

algebra word problems

View Thread Reply
- Wed, 04 Feb 2015 18:07:09 EST tkQOitI7 No.14593
File: 1423091229646.jpg -(142786B / 139.44KB, 545x677) Thumbnail displayed, click image for full size. algebra word problems
hey /math/,

Anyone have any good sites/resources for many algebra (high school level) word problems. I have a public service sector exam next month and althiough I did Calc 1 and 2 years ago in uni I find myself rusty with word problems.


Frequency Analysis of Bit Stream

View Thread Reply
- Thu, 11 Dec 2014 17:27:12 EST A69r/eB1 No.14518
File: 1418336832522.jpg -(121009B / 118.17KB, 670x667) Thumbnail displayed, click image for full size. Frequency Analysis of Bit Stream
I'm working on a project in knot theory, but my question is concerning coding schemes. When I transverse the knot, I keep track of each crossing I come across in a bit: if I go over, I set a bit to 1, if I go under, I set it to 0. So I have various strings of various lengths that might look like 000110, 101010101, 11111111, 011, 001100110011 etc.

But now, I've been asked to rank these various strings in terms of their "alternating"ness. For example, 1010101 will be the highest ranking, followed by 001100110011 and 111000111000111. Lowest ranking would PROBABLY be those with no visible pattern 0110101010101111101001. I kind of need to implement this in a program.

So my question is, is there some algorithmic process or mathematical value that can measure how close a bit stream adheres to the desired alternating pattern? My thoughts at first would be to approach this as a frequency analysis problem, but I'm open to any ideas.

tldr: can anyone point me to some references or share some wisdom concerning frequency analysis of a bit steam. Something that detects when a bit changes from one value to the next.
3 posts omitted. Click View Thread to read.
Betsy Pabberdurk - Mon, 26 Jan 2015 10:05:42 EST zIqIyS2A No.14581 Reply
Reminds me of Kolmogorov Complexity
Frederick Tillingwell - Tue, 27 Jan 2015 23:26:55 EST EOD4uY1O No.14583 Reply
It sounds like you want to calculate the length of the smallest substring that can be repeated to create the string, and rank streams by this. Of course this will consider something like 01010010101 to have the same "alternatingness" as 0001110010, I'm not sure if that's what you want. It's easy to come up with an algorithm for this that's quadratic in the length of the string. Here's an implementation in c++:

int main()
string s,prefix="";
for(int i = 0; i < s.length(); i++)
int j = i+1;
for(j; j<s.length(); j++)

return 0;
On the four examples you gave, this would output 2,4,6, and 20 respectivley. Something of rank 1 (very repetitive) would be like 0000000000.

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