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What identity is this?

  1. Feb 8, 2010 #1
    While seeing a signals example problem, I encountered this:

    cos^2 (wt+θ) = [1+cos(2wt+2θ)]

    What identity is this?
     
  2. jcsd
  3. Feb 8, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    That doesn't seem right. Looks like they missed a factor of 2:

    cos(2x) = 2cos^2(x) - 1
     
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