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Homework Help: Integrating (cos(x))^4

  1. Apr 29, 2007 #1
    I want to integrate (cos(x))^4, but I cant find a formula for (cos(x))^n in my collection.

    What is the way to integrate this?
     
  2. jcsd
  3. Apr 29, 2007 #2

    siddharth

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  4. Apr 29, 2007 #3
    Here's one way
    Use the identity cos^2(x)=(1+cos(2x))/2

    Then

    cos^4(x)=cos^2(x)*cos^2(x) = (1+2cos(2x)+cos^2(2x))/4
    =(1+2cos(2x)+1/2+1/2cos(4x))/4
    =(3+4cos(2x)+cos(4x))/8
     
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