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Homework Help: Showing fourier series of sin^2(x)=(1/2)-(cos(2x)/2)

  1. Sep 5, 2010 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations

    3. The attempt at a solution

    solving for a(0)= i did (1/2Pi)*int(sin^2(x),x,-Pi..Pi)=1/2
    b(n)=0 because sin^2(x) is an even function
    a(n)=(1/Pi)*int(sin^2(x)cos(n*x),x,-Pi..Pi)=1/2Pi((sin(xn)/n)-(.5sin((2-n)x)/(2-n))-(.5sin((2+n)x)/(2+n))) this whole thing evaluated from -Pi..Pi

    I keep getting zero although I know this is not the answer, so maybe I am messing up somewhere. Help is greatly appreciated.
  2. jcsd
  3. Sep 5, 2010 #2


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    Make sure you're not dividing by zero.
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