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Homework Help: Fourier Series (differentiation)

  1. Apr 6, 2009 #1
    1. The problem statement, all variables and given/known data

    sin(t)cos(nt) dt

    2. Relevant equations

    3. The attempt at a solution
    I tried setting u=sin(t) or cos(nt) or nt but none seems to work. Can someone give me a hint as what to set u equal to? Thanks.
  2. jcsd
  3. Apr 6, 2009 #2


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    Gold Member

    Are you trying to integrate? Over what range?
  4. Apr 7, 2009 #3
    The function is as follow:
    f(t)= 0, -pi ≤ t ≤ 0
    sint, 0 ≤ t ≤ pi

    ≤ (less than or equal to)

    I just don't know what to set u equal to, I am thinking of using integration by substitution.
  5. Apr 7, 2009 #4
    Can someone give me some hints please?
  6. Apr 8, 2009 #5


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    Homework Helper

    I would start by trying the first few cases by hand n=0, n=1, n=2, n=3, etc.. and see if a pattern develops, both on result and how to evaluate

    look at some trig formulas for angle sums & double angle may help before looking at substitution
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