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Math Help - Help finding a power series

  1. #1
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    Help finding a power series

    Using the power series of ln(1+x), find the power series of ln(x^2+1)

    I found the power series of ln(1+x) which is,
    x-(x^2/2)+(x^3/3)-(x^4/4)+...+[(-1)^(n+1)(x^n)]/n + ...

    I don't know how to find the series for ln(x^2+1); the other problems involved using the anti-derivative or derivative of the original function but that doesn't seem to work here.
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  2. #2
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    f(x) = ln(1+x) = x - \frac{x^2}{2} + \frac{x^3}{3} - \frac{x^4}{4} + ...

    so ... what is f(x^2) ?
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  3. #3
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    Ah thanks, that makes it easy. I just wasn't thinking from that perspective.
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