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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
1 posts omitted. Click Reply to view.
>>
Shitting Sullerchutch - Sat, 07 Feb 2015 16:03:40 EST ID:cMHknuu4 No.14598 Ignore Report Quick Reply
>>14587

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
>>14598
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
>>14599
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
File: 1423091229646.jpg -(142786B / 139.44KB, 545x677) Thumbnail displayed, click image for full size. 142786
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.

Thanks!
>>
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
File: 1418336832522.jpg -(121009B / 118.17KB, 670x667) Thumbnail displayed, click image for full size. 121009
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 Reply to view.
>>
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
>>14518
>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.

http://en.wikipedia.org/wiki/Discrete_Fourier_transform
http://www.math.ubc.ca/~feldman/m267/dft.pdf
>>
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="";
cin>>s;
for(int i = 0; i < s.length(); i++)
{
prefix+=s;
int j = i+1;
for(j; j<s.length(); j++)
if(s[j]!=prefix[(j-(i+1))%(i+1)])
break;

if(j==s.length())
Comment too long. Click here to view the full text.


mathematics?!?! by billyjoel - Tue, 13 Jan 2015 00:40:58 EST ID:29R5cpQe No.14559 Ignore Report Reply Quick Reply
File: 1421127658769.jpg -(799991B / 781.24KB, 2000x2597) Thumbnail displayed, click image for full size. 799991
WHAT IS DIFFERENTIAL EQUATIONS ALL ABOUT?
1 posts and 1 images omitted. Click Reply to view.
>>
Molly Blerringsore - Mon, 19 Jan 2015 02:38:13 EST ID:7MP0s8P6 No.14569 Ignore Report Quick Reply
weird ass equations that relate a value and the value's own rate of change.
>>
Nigger Dubberdet - Fri, 23 Jan 2015 15:02:12 EST ID:OlFjx/Q0 No.14572 Ignore Report Quick Reply
It's a functional equation in which there are differentials.

A functional equation is an equation, in which the unknowns are functions, instead of numbers like in algebraic equations.
Solving an algebraic equation means finding a number (numbers) that satisfy given algebraic equation.
Solving a functional equation means finding a function (functions) that satisfy given functional equation.

Generally functional equations are very hard to solve. There is no general solution to such equations. Subset of those equations, differential equations, are particularly useful, and thus intensively researched. There are general ways to solve some rather simple classes of DE, but not all of them (like the infamous Navier-Stokes equations)
>>
Phoebe Genderstitch - Fri, 23 Jan 2015 17:07:04 EST ID:E00AZouD No.14574 Ignore Report Quick Reply
Sometimes when you have a problem, you can describe it using an algebraic equation and this will give you at least one numerical value to answer your problem. It should allow you to at least narrow down your solution-search to a certain type of number.
Other times when you have a problem, you can describe it using a differential equation and this will give you at least one type of relationship between numerical values (aka functions) that will allow you to answer your problem. It should allow you to at least narrow down your solution-search to a certain type of characteristic relationship (function).

Some problems are simple and the solution will be a number. Other problems are more complex and the solution is a whole bunch of numbers that all share a certain relationship with one another.


Number one by David Barddale - Thu, 23 Oct 2014 18:57:56 EST ID:lnIBho4U No.14435 Ignore Report Reply Quick Reply
File: 1414105076933.gif -(187803B / 183.40KB, 650x510) Thumbnail displayed, click image for full size. 187803
1 is weird man.

If the basis for the value of one is wrong, all of math is pretty much fucked up right?

Also I wonder how aliens count things. Like, would they look at our system of counting things and be like wtf why is this so overcomplicated.
5 posts and 2 images omitted. Click Reply to view.
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Rebecca Poshhall - Sun, 18 Jan 2015 00:50:52 EST ID:6XbVXz0U No.14566 Ignore Report Quick Reply
>>14545
I read some of Russel's writing on the subject and I still have a hard time wrapping my head around the concept that numbers themselves are sets (or classes, as he calls them).
>>
Jarvis Hummerbick - Sun, 18 Jan 2015 10:34:32 EST ID:IYIYaVNy No.14567 Ignore Report Quick Reply
>>14566
THink of them like segments on the number line. You can have a segment going from 0 to 1. THat's 1, and it contains the 0 (empty) set. A segment going from 0 to 2 contains 0, 1 and 2, and so on. A segment that does not include 0 wouldn't exist in this system.
>>
Molly Blerringsore - Mon, 19 Jan 2015 02:36:01 EST ID:7MP0s8P6 No.14568 Ignore Report Quick Reply
I mean, like, one is just like an idea, man.


Average & Effective value by Electro M. Echanics - Mon, 12 Jan 2015 07:37:40 EST ID:Y56yfAG4 No.14557 Ignore Report Reply Quick Reply
File: 1421066260968.jpg -(52819B / 51.58KB, 640x369) Thumbnail displayed, click image for full size. 52819
Somebody here who can calculate the average value and the effective (True RMS) value of this function?
I would be Very Thankful.
>>
Electro M. Echanics - Mon, 12 Jan 2015 07:41:40 EST ID:Y56yfAG4 No.14558 Ignore Report Quick Reply
This might help: http://meettechniek.info/compendium/average-effective.html
>>
Electro M. Echanics - Wed, 14 Jan 2015 08:44:45 EST ID:Y56yfAG4 No.14563 Ignore Report Quick Reply
Nvm. Already got it !


Math Problem by Frederick Niggerhall - Wed, 10 Dec 2014 12:46:28 EST ID:J8biWsPj No.14509 Ignore Report Reply Quick Reply
File: 1418233588653.jpg -(49410B / 48.25KB, 527x640) Thumbnail displayed, click image for full size. 49410
Hi guys, I'm hoping I can get some math tips from you all. My girlfriend is a math major, and tells me that she's been having a lot of sex dreams about math recently. Sometimes, I'll find a calculator under the sheets. I'm not really a math person, so I'm not sure what to make of this or how to respond. Any tips? Thanks guys.
3 posts and 1 images omitted. Click Reply to view.
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Lillian Nunderworth - Fri, 02 Jan 2015 00:24:58 EST ID:1f/Knshx No.14548 Ignore Report Quick Reply
>>14538

I died at l'hospital.
>>
John Crisslekon - Wed, 07 Jan 2015 01:09:39 EST ID:oEhGbHUR No.14554 Ignore Report Quick Reply
>>14538
Golden post. lim x → 10 x/10
>>
James Grandcocke - Sun, 11 Jan 2015 08:47:33 EST ID:oEhGbHUR No.14556 Ignore Report Quick Reply
1420984053798.gif -(1148881B / 1.10MB, 300x300) Thumbnail displayed, click image for full size.
Here's my favorite math joke.

A Cauchy sequence is walking through town, when it sees on a wall a poster advertising a night club. "No limit night on Friday" it says. The sequence is all psyched for it, cause it's been a while since he last went clubbing, and this looked like the perfect occasion. So the sequence quickly goes back to it's place to put on it's best clothes and a nice cologne before heading to the club.
But then, when it is about to get in, the bouncer stops him and says :
Sorry, it's complete.

I just realised it may not work as well in English as it does in French. If it's the case and you're frustrated, here's a quickie.

Logarithm and Sinus wake up after a huge party. Sinus has the worst hangover ever, while Logarithm is fresh as a rose. Seeing the awful face his friend has, Logarithm says Man you really don't know your limits, don't you ?


Question about real numbers by Doris Blimmerladge - Mon, 15 Dec 2014 11:40:37 EST ID:akf5zfsA No.14524 Ignore Report Reply Quick Reply
File: 1418661637375.png -(3241B / 3.17KB, 120x119) Thumbnail displayed, click image for full size. 3241
Is there a function that can project the entire set of real numbers onto an arbitrarily sized interval within the real numbers?
4 posts and 1 images omitted. Click Reply to view.
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Beatrice Wommergold - Tue, 16 Dec 2014 15:53:58 EST ID:uPru0qmD No.14533 Ignore Report Quick Reply
>>14524
Hyperbolic tangent :
tanh(x)=(e^x-e^-x)/(e^x+e^-x) maps R->(-1,1)
atanh(x)=1/2 ln((1+x)/(1-x)) maps (-1,1)->R
a*tanh(x)+b maps R->(-a+b,a+b)
atanh((x-b)/a) maps (-a+b,a+b)->R

The nicest functions you're going to find
>>
Esther Fabberhall - Tue, 23 Dec 2014 20:47:35 EST ID:K8qJv5EF No.14542 Ignore Report Quick Reply
>>14533
^This guy's post is correct if you're looking for continuous bijections. If you're looking for just a continuous map from the reals to [a,b], you can just choose f(x) = [(b-a)/2]sin(x) + (b+a)/2
>>
Thomas Bangerham - Fri, 26 Dec 2014 18:20:04 EST ID:SlKfpVpP No.14546 Ignore Report Quick Reply
>>14524
another interesting question is whether you can project an arbitrarily sized interval within the real numbers onto the set of real numbers

answer is yes

also you can map a line of length 1 onto a cube of volume 1 etc.


Majoring in Math by Cornelius Sollerwone - Tue, 02 Sep 2014 22:17:23 EST ID:kQQi+WA1 No.14343 Ignore Report Reply Quick Reply
File: 1409710643726.jpg -(2265B / 2.21KB, 176x172) Thumbnail displayed, click image for full size. 2265
I want to know are good options for me career wise if I major in math. I just finished my first term and I don't really know what I'm doing. All I know is I enjoy math. The only thing I've had recommended to me is to become an engineer. I'm not great with electronics, computers, or mechanics. I think I could handle physics since that seems like just more applied math. I need college advice. I have a career advising appointment in a couple weeks but I would appreciate your advice!
2 posts and 1 images omitted. Click Reply to view.
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Archie Worthingfield - Sun, 07 Sep 2014 18:17:12 EST ID:xvgqavvT No.14352 Ignore Report Quick Reply
Functional programming. since you need to think like a mathematician to do it. Designing algorithms is another high demand job, especially in the finance/trading industry. Artificial Intelligence is all based of real analysis (proofs) so another field you can go into. Any stats job for the government like an environment agency, lot's of options.
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Cedric Hollertudge - Fri, 19 Dec 2014 05:04:22 EST ID:lx6v5XWF No.14540 Ignore Report Quick Reply
Analytics and machine learning is in very high demand right now, and is where a large part of the field of CS in industry is heading, due to the big data problem.

These are very math heavy. I'd recommend getting into computational math.
Learn C. Learn Python. See if you can find some open source projects and make some contributions.

Programs can be very proof-like, in my own experience.
>>
Sophie Turveyhood - Fri, 19 Dec 2014 15:50:10 EST ID:4kDzPiCs No.14541 Ignore Report Quick Reply
If you want a career in math you really have to get a PhD. That said, mathematician is regularly listed as one of the best, if not the best, job to have by many metrics. Grad school for math is always paid for. Schools will actually pay you a stipend to go there, even if you're not a top student.

Don't listen to people saying you can't get a job doing math. It has very high growth and almost no one wants to do it.


Maths tutoring by Hugh Pupperford - Sun, 14 Dec 2014 17:18:22 EST ID:8T5tyzEs No.14523 Ignore Report Reply Quick Reply
File: 1418595502621.jpg -(1288926B / 1.23MB, 1268x1800) Thumbnail displayed, click image for full size. 1288926
I wanna make some money on the side but by doing little work. I'm a maths undergrad so I was thinking of doing tutoring online. Anyone done this kind of thing before? How did you go about it? How much should I charge?
>>
Cedric Hollertudge - Fri, 19 Dec 2014 04:56:04 EST ID:lx6v5XWF No.14539 Ignore Report Quick Reply
Your skill has probably taken years of work, so you should charge something above double minimum. I've charged $20 before, and $30 is not unreasonable.

I did my tutoring at a community college, and while I was a student, there were numerous tutors who weren't. You can see if any local CCs have openings.


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