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Homework Help: Proving Reduction Formula

  1. Apr 15, 2012 #1
    If I n =integral sin (nx) dx/sinx,prove that In =2sin((n-1)x)/n-1 +In-2 for all integers n>(egual) .

    I don't know how to start...
  2. jcsd
  3. Apr 15, 2012 #2


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    Since you are given the formula, the obvious approach is to use induction.
  4. Apr 15, 2012 #3


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    sin(nx) = sin((n-1)x+x)
    =sin((n-1)x)∙cos(x) + cos((n-1)x)∙sin(x)​

    is a good place to start.
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