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Identity question

  1. May 25, 2012 #1
    1. The problem statement, all variables and given/known data

    In a worked example I have of an integration it states the integral of (cosx)^2 = the integral of (1 + cos2x)/2

    How is this equality reached?

    Is this a known identity, (cosx)^2 = (1 + cos2x)/2 ?

    Thank you.


    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 25, 2012 #2
  4. May 25, 2012 #3
    Yep, that's a very well-known identity, derived from very simple algebra from ##\cos\left(2\cdot x\right)=2\cdot\cos^2\left(x\right)-1##
     
  5. May 25, 2012 #4

    tiny-tim

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    cos(x + x) = … ? :wink:
     
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