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  1. L

    Roots

    why wouldn't you be able to?
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    Inverse Trig

    graphmatica
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    Inverse Trig

    it's not gonna really get anywhere near pi/2 max: x=0.6522, y=0.5611
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    Inverse Trig

    the lower limit is easy to find (just use x=-1). the upper limit is obv wrong. it can't rly be found, afaik.
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    Integration

    when doing the working you get to: -1/2 \int_{0}^{\pi }cos(nx)dx\\ = -1/2n [sin(nx)]|_{0}^{\pi }\\ but\ if\ n\ =0,\ you're\ dividing\ by\ zero,\ so\ n\neq 0\\ if\ n=0,\ cos(nx)=cos(0)=1\\ -1/2 \int_{0}^{\pi }cos(nx)dx\\ = -1/2 \int_{0}^{\pi }1dx\\ = -1/2[x]|_{0}^{\pi }\\ = -\pi/2\\ \neq 0
  6. L

    Integration

    n=/=0 for the condition to hold, as you can see from doing the working of the first part were there any more parts to the question? eg. find U(0), hence find U(1)?
  7. L

    progressive metal

    the only good prog/metal bands i know of are death/prog, eg. atheist, gorguts, pestilence
  8. L

    To the Mathematical Geniuses out there.

    having x in terms of t doesn't really make sense does it lol? i would think x is some constant (i.e. can't vary with t) http://mathworld.wolfram.com/AiryFunctionZeros.html if it was solvable exactly it would say there wouldn't it?
  9. L

    1972 Polynomials

    iii) since we have the 3 factors of the 3rd degree polynomial, any other polynomial must have the same factors. so, it must be a constant multiple of x(x-5)(x+5), eg. 3x(x-5)(x+5). but as P(x) is monic, the constant out the front con only be one, .'. no other polynomials iv) d is just the...
  10. L

    4U Revising Game

    sin3\theta = sin2\theta cos\theta +cos2\theta sin\theta \\ = 2sin\theta cos^2\theta + 2cos^2\theta sin\theta -sin\theta \\ = sin\theta (4cos^2\theta -1)\\ sin9\theta=sin3\theta(4cos^2 3\theta-1)\\ = sin\theta(4cos^2\theta-1)(4cos^2 3\theta-1)\\ cos3\theta = cos2\theta cos\theta -sin2\theta...
  11. L

    rio tinto big science

    v ~ rt(D) as the depth decreases, the velocity also decreases as energy is constant, and 1/2 mv2 goes down (assuming constant mass?), the mgh part must go up, so height increases C
  12. L

    4U Revising Game

    i get less than \sum_{3}^{2001}\frac{1}{r-2}-\frac{1}{r}-\sum_{3}^{2001}\frac{1}{r}-\frac{1}{r+2}\\ = \sum_{1}^{1999}\frac{1}{r}-\frac{1}{r+2}-\sum_{3}^{2001}\frac{1}{r}-\frac{1}{r+2}\\ = 1/1 - 1/3 + 1/2 - 1/4 - \sum_{2000}^{2001}\frac{1}{r}-\frac{1}{r+2}\\ = 11/12-...
  13. L

    4U Revising Game

    f(x)=ax^2+bx+c\\ f[f(x)] = a[f(x)]^2 + b[f(x)] + c \equiv [f(x)]^2\\ $equating coefficients gives a=1, b,c=0$\\ \therefore f(x)=x^2
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    Extension One Revising Game

    if you draw the parabola, and the circle, then if they're tangent, the line from the origin to @ must be perpendicular to the tangent (circle geo property). the gradient of that line is a@(@-1)/@ = a(@-1) by differentiating we find the gradient of the tangent to be a(2@-1) so a^2(@-1)(2@-1) =...
  15. L

    Area of integration, help plz

    \int_{1}^{4} (1/x^2+2x-3)dx\ ?
  16. L

    Death Metal!!!

    atheist and cynic definitely
  17. L

    Last Integration

    let x = 2sin@
  18. L

    Integration

    why not negative infinity, or -pi/2 for the inverse? (ie. isn't inverse tan not defined for pi/2? its range is -pi/2 < x < pi/2) edit: though i guess you could say that since the function is always positive, it could only be pi/2
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    Integration

    ha. maybe say that the integral gives the same value if the upper limit was (pi/2 - h) as h -> 0, h > 0 or something? i dono edit: or break the initial integral into two integrals, one of which contains the 0 limit, and the other has the pi/2 limit. so then you can divide by cos^2x for the...
  20. L

    Perms and Combs

    2nCn = (2n)!/(n!)^2 to choose the n people for each table round tables, so for each table if you hold one person constant there are then n-1 people to be arranged, which can be done in (n-1)! at each table overall: (2n)!/(n*(n-1)!)2 * (n-1)!2 = (2n)!/n2 edit: another way, is just to arrange...
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