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Mathematics

From algebra to calculus, from trigonometry to set theory, it's all here.

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  1. From basic sequences, series and calculus, to measure theory, complex analysis and more advanced topics.

    • 1.2k posts
  2. Set theory, groups and ring theory, linear algebra, and other algebra-related topics.

    • 516 posts
  3. Home to threads on more applied (but non-physical/mechanical) threads; e.g. applied group theory or statisics.

    • 464 posts
  1. Started by alejandrito20,

    If the integral is [math]\int^{\pi-\epsilon}_{-\pi+\epsilon}d\theta[/math]. where [math]\theta[/math] is a angular coordinate. In the riemman integral , i dont understand if tetha follows the path grenn in figure 1, or [math]\theta[/math] follows the path red in figure 2.

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    • 4 replies
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  2. Started by alejandrito20,

    Hello. I understand that [math]\frac{d|x|}{dx}=\theta(x)-\theta(-x)[/math] and then [math]\frac{d^2|x|}{dx^2}=2\delta(x)[/math]. But i DONT UNDERSTAND why when [math]\phi[/math] is a angular coordinate, then [math]\frac{d^2|\phi|}{d\phi^2}=2(\delta(\phi)-\delta(\pi-\phi))[/math]

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    • 1 reply
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  3. Variance is a measure of the variation in a data set, defined as Σ(y-mean(y))^2/(n-1). Is there a statistical term for the following calculation: data set time data 1 10 2 11 3 -22 4 34 5 -45 6 56 7 67 8 -78 variation between adjacent data v=(datum(t+1)-datum(t))^2 square root of v to obtain positive values of variation=v^(1/2) Σv^(1/2) median(v^(1/2))

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    • 3 replies
    • 1.5k views
  4. Started by Quetzalcoatl,

    Hi, Recently, I've been looking into the subject of information. After seeing a video on fractals I figured that a fractal is, in some sense, a dimension with missing pieces. The missing pieces can then be interpolated, if one likes, though without adding any new information. The example I've been looking at is the function f:R->R, f(x)=sin(x). It seems obvious that f being a periodic function would contain less information than some other function, say, sinc(x) (defined at zero to be equal to the limit). It also seems logical that the function f(x)=0 would have even less information than both. You could say that whenever there is less information spread …

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    • 6 replies
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  5. Started by crownedconquern,

    http://www.youtube.com/watch?v=3eXifzGOfDA Georg Cantor From Wikipedia, the free encyclopedia Jump to: navigation, search Georg Cantor Born Georg Ferdinand Ludwig Phillip Cantor March 3, 1845(1845-03-03) Saint Petersburg, Russia Died January 6, 1918 (aged 72) Halle, Germany Residence Russia (1845–1856), Germany (1856–1918) Fields Mathematics Institutions University of Halle Alma mater ETH Zurich, University of Berlin Doctoral advisor Ernst Kummer Karl Weierstrass Doctoral students Alfred Barneck Known for Set theory Georg Ferdinand Ludwig Phillip Cantor (March 3 [O.S. February 19] 1845[1] – January 6, 1918) was a German mat…

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    • 4 replies
    • 8.5k views
  6. Started by crownedconquern,

    http://www.youtube.com/watch?v=2nAycC7sGVI Educate yourself to a higher learning.... Merged post follows: Consecutive posts mergedand no,i wont baby step it for you.As you see,i done shown you all the greats and how they learned what they learned.... So.... I should be happy to know what i do.maybe if some tried,they can also feel that.Be lucky,i could have charged a trillion dollars because lets be real,the art alone in my image proves im the greatest artist ever.Now add every other knowledge and wisdom. Its weird how one image can show you everything....Hmmm why are we paying for knowledge then?

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    • 3 replies
    • 1.7k views
  7. Started by blackhole123,

    Never mind, delete this please.

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    • 0 replies
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  8. In the commutative diagrams page in wolfram, what does the [math]\phi_{i_{0}}[/math] above the arrows mean?

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    • 3 replies
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  9. Started by mar,

    Given two spheres touching at one point, would that be a surface? I think not, but I don't know how to begin to search for the proof. I thought maybe proving it isn't Hausdorff, but I'm not clear on how to go about it. Anyone can help? Sorry about the bad English, not my mother tongue...

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    • 2 replies
    • 1.2k views
  10. Started by gib65,

    I'm currently taking an online course in mathematics. One of the subjects is about interesting properties that come out of certain number series (or number patterns). Right off the bat, I'll spell out the purpose of this thread so you know where the OP is leading: I'm wondering if we can say that there's something "special" about these number series just because they bear certain interesting properties, or should we say (or prove) that there's always going to be interesting properties of any arbitrary number series no matter what it is? As an example of a number series for which an interesting property emerges, take the following: 1 + 3 = 4 1 + 3 + 5 = 9 1 +…

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    • 1 reply
    • 3.8k views
  11. Started by mehran,

    If [math] f(x) = x^3 + x + 2[/math] and [math]f(a) = 9[/math] then: Calculate [math]f^{-1}(-5)[/math] at "a". This is the question that i'm thinking of it but i can't solve it at all! Does anyone know that how i can get to the answer?

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    • 1 reply
    • 1.2k views
  12. Started by royal,

    this forum is very good for mathematics.

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    • 1 reply
    • 1.1k views
  13. Started by Abstract_Logic,

    I'm currently reading this book called Set Theory and the Continuum Hypothesis, written by Paul Cohen, which is a model-theoretic investigation of the topics. I'm trying to rediscover the proof of Gödel's Completeness theorem for myself, but I'm kind of stuck on certain details of the proof provided in the book. In the preface, the author mentioned that he did not "polish up" the final draft of the book, so many important details are left out. Although it is written for people with little to no background in propositional logic, the book assumes that one has a background in abstract mathematics, namely in Model theory. I'm only an undergraduate student not yet knowled…

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    • 1 reply
    • 1.8k views
  14. Started by Abstract_Logic,

    Let [math]X[/math] consist of four elements: [math]X= \{a, b, c, d\}[/math]. Which of the following collections of its subsets are topological structures in [math]X[/math]? [math]1. \emptyset , X, \{a\} , \{b\} , \{a, c\} , \{a, b, c\} , \{a, b\};[/math] [math]2. \emptyset , X, \{a\} , \{b\} , \{a, b\} , \{b, d\};[/math] [math]3. \emptyset , X, \{a, c, d\} , \{b, c, d\}?[/math] Are they all topological structures in X? If they are not, why are they not?

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    • 1 reply
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  15. Started by Nate Lourwell,

    Hey, all. I don't have much background yet in pure mathematics. In the meantime, I'm wondering if it would make any sense in set theory to make the set [math]kaph_{0}[/math] = {[math]n \in \mathbb{N}[/math] | [math]\aleph_{n}[/math]} and then make [math]\wp[/math]([math]kaph_{0}[/math]) = [math]kaph_{1}[/math], analogous to how [math]\wp[/math]([math]\aleph_{0}[/math]) = [math]\aleph_{1}[/math]. If that's possible, could it be continued without bound, next with [math]yodh_{0}[/math] = {[math]n \in \mathbb{N}[/math] | [math]kaph_{n}[/math]}? Merged post follows: Consecutive posts mergedI learned that a correct way to describe [math]kaph_{0}[/math], if there is one, wou…

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    • 4 replies
    • 2.1k views
  16. Started by alan2here,

    http://img693.imageshack.us/img693/3950/calcw.png http://rapidshare.com/files/325308950/operators.xlsx.html http://www.filehosting.org/file/details/91934/operators.xlsx Above is an image of a spreadsheet and two link to the spreadsheet itself. My thoughts are based on the way that multiply can even if not the most efficient way of performing the calculation can be thought of as repeated add, and power repeated multiplication. Although there are differences beyond that and other calculations just as simple and multiply that don't have names. Columns C and D of the spreadsheet show the descriptions of increment and decrement. Thease add and subtract 1. I do…

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    • 0 replies
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  17. I've just begun learning about category theory. I would love to share ideas with anyone else interested in the topic. Perhaps anyone can recommend some good learning material for it? I've started an introductory book on it, a rather small book of about 200-250 pages. I've finished the first section on general categories, subcategories, pre-categories, morphisms, and other things. I enjoy studying things at the most general level, like category theory, model theory, universal algebra, metamathematics; it intrigues me. I'm more of a generalist than a practitioner, and personally, being a man of pure ideas, I don't believe in anything merely because of its practical…

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    • 1 reply
    • 1.6k views
  18. Started by Proteus,

    If the frequencies within one, two and three standard deviations of the average are known (34,1%, 13,6% and 2,1%), can one calculate the frequency from a certain value? More specifically, I want to know if, if it is true that Ashkanazi Jews are 10% more intelligent, how much percent is gifted. Normally, that's 2,1%. If the average IQ in Ashkenazis really is 110, then the Bell curve shifts 10 points and 13,6% should have an IQ from 125 to 135. Subtract the frequency of IQs from 125-130, add the other 2,1%, and you have the frequency of giftedness. How do I know the frequency of IQs from 125-130? And please, no paranoid ragings about racialism here. I'm not Jewish m…

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    • 3 replies
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  19. So Z in that funky font is the set of integers, but is there a specific symbol for an integer or do people use Z for that as well? Also is there a symbol or a set of the integers not including 0?

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    • 2 replies
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  20. Started by JPtux,

    Okay, I have a math question that I would like help with. My teacher and I are unable to solve this problem for some reason: In 3-dimensional space line m intersect plane P in point T, and m is perpendicular to P. The points in space which are 2 inches or 4 inches or 6 inches from plane P are also 5 inches or 7 inches or 9 inches from point T lie on circles. Find the sum of the squares of the radius lengths of the circles. Our answer is 616 but the answer is supposed to be 596. Can anyone solve this? P.S. I'm sorry if I posted this in the wrong forum, I'm new. NOTE: Not a HW problem. Thanks in advance!

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    • 9 replies
    • 2.4k views
  21. Started by devrimci_kürt,

    Euler's conjecture a^4 + b^4 + c^4 = d^4 ... İs there its integer solution... my friend said, (95800)^4 + (217519)^4 +(414560)^4 = (422481)^4 COMMENTARY: ^=EXPONENT

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    • 2 replies
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  22. I'm looking at the wikipedia page on equations. But I'm getting a little confused by the different use of the terms equality, equation and identity in different situations. Amongst other stuff they say: [math] 2 + 3 = 5[/math] The equations above are examples of an equality: a proposition which states that two constants are equal. [math]x(x - 1) = x^2 - x [/math] The equation above is an example of an identity... ... Many authors reserve the term equation for an equality which is not an identity. But they said that an equality was a proposition which states that two constants are equal? What's the relationship between the three term…

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    • 2 replies
    • 9.9k views
  23. Started by Mashfiq,

    I'm choosing high schools and I want to choose a program that will be mostly about a career I want to be in. I might want a career in mathematics, but I want to know what are some specific jobs in mathematics. Can you list some? Also, what are some positive factors about those jobs?

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    • 7 replies
    • 1.9k views
  24. Started by osphere,

    Hi, does anybody know of an application of differential equations in any computer-related field? Note: Im not meaning to solve a diff. equation with a computer

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    • 1 reply
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  25. I have 2 quetions what math do they use to put a hidden picture or information in a picture like a Jpg ? And how does this work? And what math or software do they use to make picture bigger or make it clear. That say a security camera like a robbery and they use cheap camera and low quality .What math would they use to make it bigger and clear . Low quality and small picture. http://www.blogcdn.com/www.joystiq.com/media/2008/12/gamestoprobbery.jpg I thought the video enhancing department of the police station use adobe photoshop ? Some one was saying there is no limit to video enhancing still image or moving image it is just more math. How does thi…

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    • 6 replies
    • 2.4k views

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