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Factoring Cosine

  1. Sep 27, 2015 #1
    The Question:

    My Attempt:

    I use the 'Double Angle Formula' to get to the second line. Then multiply the sigma-x into whats in the brackets, then factor out at the end. I'm not sure how I reach the answer thats provided with the solution. Any help would be appreciated.

    Thank You.
  2. jcsd
  3. Sep 27, 2015 #2


    User Avatar
    Gold Member

    You've pretty much already got the answer. Just expand that last line and re-arrange.
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