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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 bob000555,

    Let's say we define a set [math]S[/math] in the following manner. [math] 0 < S_0 < 1 [/math] [math] S_n = (1-S_{n-1})^x[/math] If we take the example [math]S_0 = \frac{1}{2}[/math] and [math]x = 3[/math] then the set apears to not converge and to follow no set pateren, is this chaos?

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    • 1 reply
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  2. Started by Killjoy,

    What are people's opinions on which are the most important theorems in mathematics? By important I mean those with the most significant consequences both in pure and applied mathematics (not just obscure results that happen to be interesting to a few individuals). I would suggest the the Pythagoras Theorem should be up there. What else?

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    • 6 replies
    • 2.2k views
  3. Started by Kaeroll,

    Hi all Have a quick question... I'm writing up my year's project work, and shockingly enough it involves a handful of straight line graphs. Excel kindly provides me with a line of best fit and its corresponding equation, along with a value called R-squared. (Mine is 0.537... not too good) I know this is a measure of how good the fit is, but I'm not sure how to explain this in my write-up. I won't need detail on it, just a brief statement to the tune of "The correlation isn't very good". How should I refer to this R-squared value? I know very little about statistics. Cheers Kaeroll

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    • 4 replies
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  4. Started by Megabrain,

    I am amused to consider that I find nothing in nature that exists as a negative quantity, for example, a tree cannot have a minus quantity of leaves, if it started with 3000 leaves and now has 2000 it does not have -1000 leaves it has 2000 leaves. leaving aside 'debt' which is a man made concept/quantity, where if anywhere does negative exist in nature, such things as 'negative voltage' is merely a reversal of polarity or direction. Travelling at -3mph is actually travelling at 3 miles per hour in a different direction, negative is an opposite direction and not an opposite to positive in any true sense. In the sum 5-3=2 there is no negative quantity, there is …

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    • 20 replies
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  5. Started by rakuenso,

    Is there a name for a family of parametric curves [math] x(t) , y(t) [/math]where... [math](\frac{dx}{dt})^2+(\frac{dy}{dt})^2=1[/math]? If possible, generalized to multiple dimensions... [math](\frac{dx_1}{dt})^2+(\frac{dx_1}{dt})^2+...+(\frac{dx_n}{dt})^2=1[/math]

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    • 0 replies
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  6. I have a surface Z, which is a function of the variables x1,x2,x3... etc. ie. Z(x1,x2,x3...) I have a point Z0 and a point Z1 which corresponds to some point on this surface. There is some line M that connects Z0 and Z1 on the Z surface, note that M does NOT have to be the shortest distance. However, M must be bound to the surface Z. How do I find the length of the line M on this surface? Ideally the expression would be somehow linked to the directional derivative, IE. I've been thinking of slicing the line M into tiny little components, and taking the directional directive at each point of M, the integrating with respect to.. something (maybe dx1, dx2, dx3... …

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    • 9 replies
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  7. An open interval is an interval that does not include its end points. http://mathworld.wolfram.com/OpenInterval.html What I don't understand is why is it called an open interval?

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    • 4 replies
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  8. Started by Flanker,

    Hello, I have a question about the change of radix, for example: Convert 1020304 base 10 into base 7: 1020304 / 7 = 145757 r 5 145757 / 7 = 20822 r 3 20822 / 7 = 2974 r 4 2974 / 7 = 424 r 6 424 / 7 = 60 r 4 60 / 7 = 8 r 4 8 / 7 = 1 r 1 1 / 7 = 0 r 1 => 11446435 There is a tip to divide a big number with a little number?, is posible with a simple calculator get the remainders from a divition like that?

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    • 1 reply
    • 1.1k views
  9. Started by Shadow,

    Hey all, so, I was at this math contest last Tuesday. The contest consisted of 4 question, of which one was geometry. I had absolutely no clue on how to solve it, so I was wondering if anybody here could help me. We have a triangle [math]ABC[/math], which is not isosceles. Let [math]x[/math] be a line that bisects the angle [math]ACB[/math], [math]y[/math] be the perpendicular bisector of [math]AB[/math], [math]h_a[/math] be a line perpendicular to [math]BC[/math] and passing through [math]A[/math] and finally [math]h_b[/math] be a line perpendicular to [math]AC[/math] and passing through [math]B[/math]. Let [math]K \in x \cap y[/math], [math]P \in KC \cap h_a[/ma…

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    • 0 replies
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  10. Would You mind telling me how to install plugin vbLatex for vBulletin? Could you tell... step to step. Thanhs a lot. K19:embarass:

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    • 7 replies
    • 8.3k views
    • 1 follower
  11. Started by coke,

    Anybody want to try this problem? I know the answer and how to do it, I'll tell you later. Anyways... You have a random number generator, that generates the numbers 1-5 randomly (equal probability of each). You need to make a random number generator out of it that generates the numbers 1-7 randomly (equal probability of each). How do you make it out of the first generator? For example, you can take a number from the first one, and run it through the first one 5 more times, and say if you get some answers tell the generator to start over again, etc.

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    • 12 replies
    • 3k views
  12. Started by cameron marical,

    i know this is a reall general and broad question{and stupid/new to this world sounding}, im just wondering what kind of answers ill get. i love math, but when i ask myself this question, i seem to lack the answer.

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    • 34 replies
    • 6.4k views
  13. Started by bambelbitz,

    Hey to everyone here in this forum. I'm new here and I have got a question concerning the exterior derivative and the Lie derivative. I have to show the following: (I searched for them for four hours on the net but no site is giving me a proof of it) These two I have to show for all p-form (p is between 0 and m if M is a manifold of dimension m) This is the formula for the exterior derivative which I have to show: Sorry I don't know why the picture are not shown here. Hope someone can help me!!! Any help is appreciated! If you have a book or a site where you have found one of these proofs let me know! Thanks

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    • 2 replies
    • 2.7k views
  14. Started by Henrik,

    How is it a paradox? Is it just seems to be parsing the model of reality incorrectly? Or what?

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    • 11 replies
    • 2.3k views
  15. Started by TheUnknown,

    i = [math]\sqrt{-1}[/math] i[math]^{4}[/math] = [math]\sqrt{-1}[/math][math]^{4}[/math] = 1 [math]\sqrt[4]{1}[/math] = i = 1 Therefore [math]\sqrt{-1}[/math] = 1, but that would mean that 1*1 = -1 Which is impossible. How is this? Did I make a miscalculation? Or is this really a paradox?

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    • 10 replies
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  16. I keep doing the problem like the formula says but I keep getting the wrong answer The problem is m^2-3=-m 21. m^2 -3=-m m^2 +m-3=0 m^2/1 +m/1=3/1 m^2+(m/2)^2=3 m^2 +m+0.25=3 + 0.25 m^2 + m +0.25=3.25 (m+0.5)^2= square root of 3.25 m+0.5= square root of 3.25 and thats where I get stuck because when I look in the back I see im way off. Can someone explain what im doing wrong. It would be a big help.

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    • 16 replies
    • 4k views
  17. Started by --00--,

    Does anybody have any ideas on how to work out [imath]\sqrt{0.9}[/imath] without a calculator (to approx 10 d.p.)? I know there are a few methods for working out for working out square roots by hand, but i was wondering if there was a cleverer/easier way of doing it.

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    • 20 replies
    • 44.8k views
  18. Started by Poobah,

    could this be a typo? in a question sheet? 2cosecx-1=0???

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    • 5 replies
    • 1.9k views
  19. Started by Poobah,

    I have no clue how to do this one... let a= -1+i, b=-2-i, solve for z. b*=complex conjugate of b z-b*=Im(a^2/(2b+i))

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    • 1 reply
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  20. Started by Vay,

    can someone explain how it expands or contracts on a complex plane? The first time i tried to see how it works, i used real numbers, but is there a difference or am i doing something wrong because the triangles as a result are not similar.

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    • 0 replies
    • 959 views
  21. What do you think about this podcast from the American Military university?

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    • 6 replies
    • 1.8k views
  22. hey, im a freshman in highschool, so im barely educated in too much complex math, but i want to learn it all{ i know, big statement}. im in an algebra 1 class right now. any good book suggestions teaching this to calculas math? or anything higher than calculas? thanks.

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    • 3 replies
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  23. Started by ajb,

    Let us work in the [math]\mathbb{Z}_{2}[/math] graded category. A Loday algebra is a "crippled" or "wonky" Lie algebra. That is it satisfies the bracket satisfies the Jacobi identity, but is not skew symmetric. An interesting question is if there exists a homotopy version. I suspect that one can consider "crippled" [math]L_{\infty}[/math] -algebras. So, a series of brackets that satisfy higher Jacobi identities, but do not have a symmetry property. Any body seen anything like that? A differential over such an algebra would also be straight forward to define. I myself have defined notions of a differential [math]L_{\infty}[/math]-algebra and a differen…

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    • 0 replies
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  24. Started by dpt90,

    first of this is part of my assignment , secondly please forgive me if i posted this in the wrong place.... this just seemd like the place to post this. i have 2 curved graphs S and V..... and one is increasing more rapidly than the other over a distance at one points in the graph and the other after a few values starts to increase faster than the other one. how would i find the values for the distance where S Gradient is ascending faster than V, and when V Gradient is ascending faster than S...... i only need a push in the right direction please.... i hope i said that coherently . my teacher said to use change in y/ change in x or something but im lost really..…

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    • 10 replies
    • 2.3k views
  25. Started by Shadow,

    Hey all, The title's a little misleading, what I'm really wondering about is, can a cube and a cuboid have the same areas AND volumes, without the trivial solution of a=b=c=s, where s is the side of the cube. I did some calculations, however I have absolutely no idea if they're right, and to be quite honest I sort of doubt it. If a, b and c are the sides of a cuboid, and s is the side of a cube, this is what I came up with: http://i44.tinypic.com/oi9e75.jpg Cheers, Gabe

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    • 7 replies
    • 2k views

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