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probability by Phoebe Cliddlesure - Wed, 18 Mar 2015 01:56:40 EST ID:DYY7KYkl No.14645 Ignore Report Reply Quick Reply
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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?
5 posts and 2 images omitted. Click Reply to view.
Lillian Smallfoot - Wed, 18 Mar 2015 06:23:21 EST ID:Qzq4CNd5 No.14651 Ignore Report Quick Reply
whoops. sorta assumed this was prog and forgot which board I was on when I saw rand(). Glad to help. nb
Esther Crishston - Wed, 18 Mar 2015 23:15:38 EST ID:JDIWTmrz No.14652 Ignore Report Quick Reply

Because it's the 5 fold convolution of the uniform distribution. The result will be a quartic distribution
Cuntfuck - Thu, 19 Mar 2015 16:07:14 EST ID:xgdLZpNp No.14656 Ignore Report Quick Reply
Because that's not how random works?
Priscilla Hezzlemore - Sat, 21 Mar 2015 06:14:50 EST ID:qz3c7Bt+ No.14658 Ignore Report Quick Reply
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You must use combinatorics.
Priscilla Hezzlemore - Sat, 21 Mar 2015 06:20:27 EST ID:qz3c7Bt+ No.14659 Ignore Report Quick Reply
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oops that last part was not up to /math/ standards

Beginnings by Nemywa - Thu, 19 Mar 2015 15:26:51 EST ID:lxw6acDK No.14654 Ignore Report Reply Quick Reply
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>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 by StellarCir - Sun, 15 Mar 2015 04:05:09 EST ID:M7BdweVS No.14637 Ignore Report Reply Quick Reply
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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?
Lillian Fannerdale - Mon, 16 Mar 2015 08:56:29 EST ID:4/hffjyH No.14639 Ignore Report Quick Reply
Depends how you define 'maths'. The fist step would be understanding that 5 apples and 5 bricks have some quality in common, or perhaps showing them 2 quantities of the same object and giving them treats if they add them. Chimps have a better working memory than us in tests which use numbers, but they use them as arbitrary symbols. There's a lot of conciusness involved in treating maths as an end in and of itself
Lillian Fannerdale - Mon, 16 Mar 2015 08:58:54 EST ID:4/hffjyH No.14640 Ignore Report Quick Reply
The thing about chimp sign language is that it's all repetition, any claims of them making new words always turn out to be overhyped. It's language without linguistics, in general the most animals can do in this realm is relate an actual object with some kind of symbolic representation of it, impressive but very far from any abstract logic
Fanny Wittinghut - Mon, 16 Mar 2015 15:53:08 EST ID:SpD/fp2u No.14641 Ignore Report Quick 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 15:54:04 EST ID:SpD/fp2u No.14642 Ignore Report Quick Reply
And you left out octopus, wtf.
Fanny Wittinghut - Mon, 16 Mar 2015 15:57:41 EST ID:SpD/fp2u No.14643 Ignore Report Quick Reply
Actually you didn't leave out octopus, apparently I am drunk

Help learning gcse maths by Shitting Lightridge - Sat, 03 Jan 2015 10:45:28 EST ID:NxPbw8hD No.14549 Ignore Report Reply Quick Reply
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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 ID:ev+cRfEi No.14555 Ignore Report Quick Reply
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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
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Hugh Collerfoot - Thu, 05 Feb 2015 22:24:09 EST ID:Gj+82UIb No.14595 Ignore Report Quick 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 ID:JDIWTmrz No.14638 Ignore Report Quick 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

Analysis by William Gissleville - Thu, 26 Feb 2015 17:18:10 EST ID:Yi4ytYm1 No.14616 Ignore Report Reply Quick Reply
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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.
4 posts omitted. Click Reply to view.
Charles Blathergold - Sat, 28 Feb 2015 15:32:06 EST ID:Gj+82UIb No.14623 Ignore Report Quick Reply

Also, you may be interested in these short(ish) books to help you write proofs.
William Crucklemeck - Sun, 01 Mar 2015 22:15:42 EST ID:e+7yrnP7 No.14624 Ignore Report Quick Reply
Unless you are talented and bright, Rudin's book is a very rough intro to analysis. You have to treat the entire book like an exercise, rather than just expecting the author to help you learn the material.

I would go only go through it after going through a BS level text first, so then you have some familiarity with what's going on.

But if you are devoted/intelligent enough it will certainly benefit you most
Nigel Figgleputch - Wed, 04 Mar 2015 07:17:41 EST ID:weDVNH8d No.14627 Ignore Report Quick 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 ID:JDIWTmrz No.14632 Ignore Report Quick Reply
Read Baby Rudin. All the exercises are online.
Hedda Niggerford - Mon, 09 Mar 2015 22:44:02 EST ID:Gj+82UIb No.14633 Ignore Report Quick Reply
>group theory

You can also pirate the Princeton Companion to Mathematics, which covers literally everything. There's plenty of recommended texts in it to dive further into material

just sayin by Nigger Drunkinstock - Thu, 05 Mar 2015 23:48:50 EST ID:PmLosP1P No.14628 Ignore Report Reply Quick Reply
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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 ID:F9AJX/Os No.14629 Ignore Report Quick 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 ID:nxCnniYW No.14630 Ignore Report Quick 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 by Edwin Pimmleman - Mon, 23 Feb 2015 22:03:13 EST ID:zBSUDYOt No.14612 Ignore Report Reply Quick Reply
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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
Comment too long. Click here to view the full text.
Phoebe Blillerridge - Tue, 24 Feb 2015 22:30:13 EST ID:N0lLaAL+ No.14613 Ignore Report Quick Reply
It would be helpful if you just typed out in paint what the equation is rather than using free draw. Right now i can hardly read the left side of the equation and have to trust your post to tell me exactly what it is we are doing
Basil Donderwell - Wed, 25 Feb 2015 00:16:01 EST ID:zBSUDYOt No.14614 Ignore Report Quick Reply
1424841361224.png -(2779B / 2.71KB, 444x245) Thumbnail displayed, click image for full size.
Well I solved but this problem is also hard for me here it is in paint also I'm practicing for a placement test and im using a guide online can't remember if links are allowed here but its number 17 in this link https://www.barton.edu/pdf/math/practice-math-placement-test.pdf

also its not for this school
Basil Donderwell - Wed, 25 Feb 2015 00:18:51 EST ID:zBSUDYOt No.14615 Ignore Report Quick Reply
Fuck meant 16 but yeah can't do 17 either =\
Jack Hammerfoot - Sat, 28 Feb 2015 03:01:48 EST ID:e+7yrnP7 No.14619 Ignore Report Quick 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 ID:e+7yrnP7 No.14620 Ignore Report Quick 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

guides/tutorials by Betsy Pockville - Thu, 26 Sep 2013 03:14:08 EST ID:Mpud+AHb No.12970 Ignore Report Reply Quick Reply
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anybody have good simple tutorials/guides on using SAS and or LATEX?
4 posts and 1 images omitted. Click Reply to view.
Sophie Blatherstone - Thu, 29 Jan 2015 09:57:46 EST ID:Nd1rFVLA No.14584 Ignore Report Quick Reply
I do. Сaм вeдь русский.
Nell Sidgewon - Mon, 02 Feb 2015 23:28:54 EST ID:3MAA0GNs No.14591 Ignore Report Quick Reply
Don't both with LyX. I started on it and it's actually more trouble than regular LaTeX. Just use this :

Nigger Nuddlehedging - Fri, 13 Feb 2015 01:10:35 EST ID:UXwZVF0/ No.14606 Ignore Report Quick Reply


Also, use gummi. It generates a pdf view of your document as you type, so you can see the changes you're making.

Walter Drendlekidging - Sat, 21 Feb 2015 13:38:57 EST ID:Dk8yywxc No.14610 Ignore Report Quick 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 ID:yFfkLiLW No.14611 Ignore Report Quick 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 by Adly Assaf - Wed, 17 Dec 2014 01:02:18 EST ID:XuUSwld1 No.14534 Ignore Report Reply Quick Reply
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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.
Phoebe Wablingwere - Wed, 17 Dec 2014 03:39:19 EST ID:uPru0qmD No.14535 Ignore Report Quick Reply
You missing the key part: GCD(a,b)=1 therefore if x|a and x|b then x|GCD(a,b), a contradiction
Charles Murdford - Thu, 15 Jan 2015 19:56:16 EST ID:h2IBC+4I No.14564 Ignore Report Quick 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 ID:h2IBC+4I No.14565 Ignore Report Quick Reply
made a mistake meant to say aa=p_(1)...p_(n)p_(1)...p_(n)
Fuck Chundlechod - Fri, 13 Feb 2015 00:01:12 EST ID:lx6v5XWF No.14605 Ignore Report Quick Reply
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This one's from The Book!

math question by jim - Thu, 22 Jan 2015 14:43:35 EST ID:yDDqWeTL No.14571 Ignore Report Reply Quick Reply
File: 1421955815798.jpg -(9639B / 9.41KB, 240x240) Thumbnail displayed, click image for full size. 9639
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
Ian Bockleridge - Thu, 29 Jan 2015 20:29:03 EST ID:mfk1g/VQ No.14587 Ignore Report Quick Reply
a) Revenue is the total amount money earned after selling x stereos. Each stereo costs p(x), so R(x) = x*p(x) = 1000x-x^2

b) Profit is the total amount of money earned minus the total cost of production; P(x) = R(x) - C(x) = 980x - x^2 - 3000

c) To know this answer, you must find out at which x does the function P(x) maximize. First, we find out dP/dx (or P'(x), I don't know what notation you use):
dP/dx = -2x + 980

When P is at a max, dP/dx = 0 (just trust me on this, I cba to explain it fully. It's in every 11/12th grade mathbook ever made); 0 = -2x + 980 > x = 490

d) Just substitute x for 490 in the profit equation: P(490) = 237 100 $
Shitting Sullerchutch - Sat, 07 Feb 2015 16:03:40 EST ID:cMHknuu4 No.14598 Ignore Report Quick 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 ID:tX1aaDR5 No.14599 Ignore Report Quick 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 ID:tX1aaDR5 No.14600 Ignore Report Quick 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 by Walter Pettinglurk - Wed, 04 Feb 2015 18:07:09 EST ID:tkQOitI7 No.14593 Ignore Report Reply Quick Reply
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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.

Hugh Collerfoot - Thu, 05 Feb 2015 22:11:17 EST ID:Gj+82UIb No.14594 Ignore Report Quick Reply
Find a torrent of this or buy it http://www.amazon.ca/Solve-Word-Problems-Algebra-Edition/dp/0071343075

Frequency Analysis of Bit Stream by Emma Gandleforth - Thu, 11 Dec 2014 17:27:12 EST ID:A69r/eB1 No.14518 Ignore Report Reply Quick Reply
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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.
1 posts omitted. Click Reply to view.
Edwin Blenkinwell - Sun, 14 Dec 2014 10:44:08 EST ID:hudlvJsh No.14521 Ignore Report Quick Reply
What you code do:
For a bit string X
replace all 00 in X with 0
replace all 11 in X with 1
The then greater length of X the greater "alternating"ness
You can of course also normalize this by dividing by the original length of X
Ian Sittingstid - Sun, 14 Dec 2014 16:44:15 EST ID:nc9XL7V5 No.14522 Ignore Report Quick Reply
You could look into using hamming distance, which i think is what the post above me was talking about.

Alternatively you could look for occurrences of a sub-string (Your pattern) in the string, possibly using reg-ex's for this.

If your looking for like, any arbitrary pattern, a state machine would be your best bet i think.

I'm not sure what exactly your asking for here man, so i hope this helps
Betsy Pabberdurk - Mon, 26 Jan 2015 10:05:42 EST ID:zIqIyS2A No.14581 Ignore Report Quick Reply
Reminds me of Kolmogorov Complexity
Betsy Guvingspear - Mon, 26 Jan 2015 13:51:36 EST ID:JDIWTmrz No.14582 Ignore Report Quick Reply
>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

That's just a Discrete Fourier Series. Read/skim through an EE book on Linear Systems and Signals and/or DSP.

Frederick Tillingwell - Tue, 27 Jan 2015 23:26:55 EST ID:EOD4uY1O No.14583 Ignore Report Quick 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++)

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