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Thread: Can somebody show me how to go from one expression to the other?

  1. #1
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    Can somebody show me how to go from one expression to the other?

    I have the following expression:
    $\displaystyle -\frac{1}{4}\cdot\frac{(-2+n\cdot sin(\pi n)\pi + 2cos(\pi n))\cdot sin(nx)}{n^3}$

    I need to rewrite it and end up with:
    $\displaystyle \frac{sin((2n-1)t)}{(2n-1)^3}$
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  2. #2
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    Re: Can somebody show me how to go from one expression to the other?

    What is t? Or should it be $\displaystyle \pi$?
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    Re: Can somebody show me how to go from one expression to the other?

    Quote Originally Posted by richard1234 View Post
    What is t? Or should it be $\displaystyle \pi$?
    Nevermind, I figured it out on my own.
    It's part of a fourier series. I found out that for all $\displaystyle n=even$ the expression will yield zero and for all $\displaystyle n=uneven$ the expression will yield $\displaystyle \frac{sin(nt)}{n^3}$

    For $\displaystyle n$ expressed as an uneven integer, we can rewrite it as $\displaystyle n=2k-1$ thus if you insert this and change $\displaystyle k$ to $\displaystyle n$ in the new expression, the work is then complete. Sorry for not writtign my question that good, my bad.
    Thanks from topsquark
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