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Math Help - Derivatives and inverse

  1. #1
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    Oct 2009
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    Question Derivatives and inverse

    I need to find the derivative of
    a) g(x) = (x-e^(-2x)) / (1-x*e^(-2x))

    b) f(y) = cos[sqrt(x^2 + 4)]

    For a) i get up to

    [(1 + 2e^-2x)(1 - xe^-2x) + (e^-2x - 2xe^-2x)(x - e^-2x)] / (1 - xe^-2x)

    but it's supposed to somehow be simplified to -2(x+1) / (x-1)
    I don't know how to get here from my answer.

    for b) I just need help finding the inverse and then I can find the derivatives myself
    Last edited by mr fantastic; October 28th 2009 at 03:13 AM. Reason: Deleted duplicate question answered elsewhere.
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