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Homework Help: Convolution fourier series question

  1. Dec 28, 2009 #1
    P_r is defined as:
    [tex]P_r(x)=\frac{1-r^2}{1-2r\cos x +r^2}[/tex]
    [tex]P_r(x)=\frac{1-r^2}{1-2r\cos x +r^2}=\sum_{n=-\infty}^{\infty}r{|n|}e^{inx}[/tex]
    which is continues

    i need to prove that:

    the solution says to use the convolution property
    [tex]c_n(f_r)=c_n r^{|n|}[/tex]

    but i cant see how the multiplication of those coefficient gives me the
    expression i needed to prove


    i only got the right side not the left integral

  2. jcsd
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