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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 BigMoosie,

    I am working on some problems on particle dynamics and I keep making errors originating from the following: [math]\int \frac{1}{x} = log_e x[/math] or [math]\int \frac{1}{x} = \int \frac{-1}{-x} = log_e -x[/math] Why is it that there are two solutions and how can I identify which is the correct one to follow?

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    • 7 replies
    • 3.1k views
  2. Started by caseclosed,

    find the point of intersection of the lines x=2t+1, y=3t+2, z=4t+3, and x=s+2, y=2s+4, z=-4s-1, and the find the plane determined by these lines. I don't know what to do...

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    • 4 replies
    • 1.8k views
  3. Started by Martin,

    John Baez (mathematician interested in quantum gravity, category theory and divers other stuff) has a kind of sporadic blog called This Week's Finds in Mathematical Physics. And TWF #239 just came out Baez and lady were in China for the summer and have some neat photos of life and sights you might want to look at scroll down a couple of days here http://math.ucr.edu/home/baez/diary/august_2006.html'>http://math.ucr.edu/home/baez/diary/august_2006.html to the start of the Shanghai and Suzhou pictures TWF 239 is partly about the origins of mathematics in the Mideast around 8000 BC with some clay tokens. Baez shows some photos of the tokens here http://math.u…

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    • 0 replies
    • 1.3k views
  4. Started by albertlee,

    say, on a graphic of cubic function, there is a root at 2, a y point on 8 when x is 1, and another on 8 also when x is -1, and when x is 0, y = 8. 1) if I solve this by: (x-2)(ax^2+bx+c).... I get an answer because I can solve a, b, c by 3 different simul equations. but 2) if I solve this by: (x-2)(ax+b)(x+c), I get more answers because when I try to solve c, I get a quadratic equation for it, which means c can have 2 values...... but this cannot be possible, since c can only be one value as a root. plz help

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    • 2 replies
    • 1.7k views
  5. Started by Zareon,

    Can anyone please explain why gcd(n,m)=gcd(n-m,m)? (n>=m) It's like everyone assumes it because, apparantly, it's so obvious, but I don't see it.

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    • 4 replies
    • 2.2k views
  6. Started by civan,

    An Interesting Animation About Holy Quran http://www.simetrikkitap.com/binary/binary.html

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    • 8 replies
    • 1.7k views
  7. Started by betelgeuse,

    a=3^b b^a-a^b=0 a.b=?

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    • 8 replies
    • 1.9k views
  8. Started by Lars,

    I need help with a maths assignment, Im having a brain block and I have a feeling that the forumula is really easy and Im just having a bad day, but this is basicly what I need to find out. (REALLY simple stuff) I have a rectangle I need to find the volume for, and I only have the length and width measurements for it. I need to find the height to calculate the volume (As Im sure you all know) volume is; width X length X height, so what have I missed, Am I having a brain block or is it something more complex? Please help, its due tomorrow. Its pretty much this, Looks simple but im stumped...

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    • 3 replies
    • 1.3k views
  9. Started by blackhole123,

    (taken from http://www.esmerel.com/circle/numeracy/tricks.html) this is news to me

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    • 6 replies
    • 2.2k views
  10. Started by Sarahisme,

    Hello all, I am completely new to this stokes theorem bussiness..what i have got so far is the nabla x F part, but i am unsure of how to find N (the unit normal field i think its called). any suggestions people? i get that nabla x F or curl(F) = i + j + k cheers -sarah

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    • 14 replies
    • 3.4k views
  11. Hey all, I was sent an AS Maths preparation/revision booklet for me to go over and complete questions in before i go back to school. After one of the questions, it gives a random puzzle and I am stumped. I havent been told how to do it before. It says that a cubiod has a volume of 7.5cm3, a total surface area of 26cm2 and the total lengths of all its sides is 26cm. I am told to give the dimensions of the cuboid. I have absolutely no idea on how to do this. I can find the volume etc from the dimensions easily, but i dont know how to do it in reverse. Could someone please shed some light on how i would go about doing this. Thanks

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    • 3 replies
    • 2.4k views
  12. Started by the tree,

    Say a scientist gave you a set of values of A from an experiment of changing the value of B. You're told that the experiment has been repeated and that the values of A are consitent (with an acceptably tiny margin of error) each try. At first glance there is nothing as simple as the value of A just going up as B increases but as there is definately a connection so the scientist has asked you, the mathematician, to describe the relationship between these to variables. How do you begin attacking this problem? Where do you start when all you have is a sheet of numbers?

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    • 3 replies
    • 1.7k views
  13. Started by Sarahisme,

    Hi all, i am little puzzled by these questions, not sure if i am doing it correctly or just blundering along! what do you guys think? cheers Sarah for (a) i get: [math] I = \int_0^{2\pi}\int_{-1}^1f®rdrd\theta [/math] for (b) i get: [math] I = \int_{-\pi/4}^{\pi/4}\int_{\frac{-1}{cos\theta}}^{\frac{1}{cos\theta}}f®rdrd\theta [/math] for © i get: [math] I = \int_{0}^{2\pi}\int_{0}^{cos\theta}f(tan\theta)rdrd\theta [/math] if people want the working just shout, i just don't have quite enough time to put it up at the moment. -sarah

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    • 17 replies
    • 2.8k views
  14. Started by Sarahisme,

    Hello, I am confused by what this question is asking, and i was wondering if anyone could suggest the best way to approach it? Thanks sarah

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    • 12 replies
    • 2.4k views
  15. Started by Primarygun,

    Given, [Math]S=x^{3}y^{2}z[/Math] and [Math]x+y+z=1[/Math] Determine the greatest value of S. How do we start this type of question? I started with [Math]S=xxxyyz[/Math]where there are six terms; used AM-GM and found that x=y=z, I know it's wrong, but why? Then I think it occurs because there's no limits of them. Therefore, I sub [Math]z=1-x-y[/Math] So [Math]S=(1-x-y)(x^{3}y^{2})[/Math] But there's no clear solution for me. What should I do next?

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

    I got a notes but have difficulty in interpreting all the material there. Later give you. It's about using Vieta's formula and Newton-Girard Formula to prove/find the general solution of sequence? I'v read some other material but most didn't give me a clear concept as they don't have relevant detail. The closer one is telling that the general solution for one linear equation and two equations. How can I find that of three?

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    • 2 replies
    • 1.3k views
  17. Started by Primarygun,

    Given, [Math]S=x^{3}y^{2}z[/Math] and [Math]x+y+z=1[/Math] Determine the greatest value of S. How do we start this type of question? I started with [Math]S=xxxyyz[/Math] where there are six terms; used AM-GM and found that x=y=z, I know it's wrong, but why? Then I think it occurs because there's no limits of them. Therefore, I sub [Math]z=1-x-y[/Math] So [Math]S=(1-x-y)(x^{3}y^{2})[/Math] But there's no clear solution for me. What should I do next?

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    • 1 reply
    • 982 views
  18. Started by Primarygun,

    Here is a rather tough problem for me. I appreciate any suggestion for the solution from any of you cause I really don't have any idea.

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    • 0 replies
    • 1.1k views
  19. Started by Truth_Seeker,

    I am trying my hardest to come up with an example of an actual infinite, versus just a potential infinite, without having a platonist rationale. One book I was reading suggested the number of positions that, say, an electron could occupy on a yardstick. I guess it could truly be anything: a ping pong ball and football field, or even a golf ball and a line segment 1 mm longer than the golf ball's diameter. But, my hangup in this, is if there are truly an infinite number of points it could occupy, then how could you roll that ball the entire length of your measure and cover every position if it truly had an infinite number of positions? Like I said, my thinking is m…

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    • 9 replies
    • 1.9k views
  20. Started by Primarygun,

    For sequence' a n = a n-1 + a n-2 We first assume that a n has a general form of b^n. Then, we put it into the sequence equation and get a quadratic one. It will be ok for me if the final solution for the a n be that form. But normally, if there exists two different roots, the final solution indeed is in the form of (C b^n + D f^n) where they are arbitrarily assigned. Why do we assume the incorrect form but getting the correct answer? Any comments Please!

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    • 4 replies
    • 1.5k views
  21. hello, i could never work out this problem, and i am fed up it now, hope my question is clear!! thank you

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    • 2 replies
    • 1.2k views
  22. Started by scidude,

    How do you find the volume of a human body in a simple, original and accurate way? ...please do not say, get into the bath.

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    • 16 replies
    • 2.6k views
  23. Started by YT2095,

    I`m probably missing something simple here, but here goes: you`re in your Lab and make Chemical X. you don`t know what the properties of this chem X is. you get a phone call that requires you to leave the lab and this chem. now it`s either Stable or it isn`t, it`ll be just the same when you get back, OR it`ll be a disaster area! you Don`t Know about Chem X though. it`s one of 2 outcomes only. are you taking a 50/50 chance by leaving it?

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    • 23 replies
    • 4.4k views
  24. Started by Primarygun,

    f(x+y)= f(x)f(y) If we take log for both sides, we have g(x)= g(x) + g(y) by letting g=log f Then, after a series of calculation and checking, we have f(x)= a^ (cx) I have a few questions dealing with the log. Can I choose any base, for example 10? Must a=e where it is the natural log.? Last, I am confused with the use of fixed point, or perhaps I even don't know the complete definiton of me, hence, finding myself incapable of doing this kind of calculations. EDIT: I am very interested and enthusiastic for functional equation. However, I can't find any books related to this topic or subtopic. I've checked algebra, statistics. Does it belong to Discrete maths …

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    • 7 replies
    • 1.9k views
  25. Started by mike2313,

    Parallelogram ABCD has diagonal AC equal in length to side AB. CD is produced to E so that D is between E and C. If angle BAC = 30 degrees, find the size of angle ADE Please Help Thanks in advance

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    • 7 replies
    • 3.3k views

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