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Homework Help: How to factor cos22X + cos2X = 0

  1. Nov 8, 2008 #1
    How do I factor this?

    cos22X + cos2X = 0
  2. jcsd
  3. Nov 9, 2008 #2


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    Welcome to PF!

    Hi Aceradonia ! Welcome to PF! :smile:
    Well, cos22X is the same as (cos2X)2,

    so you can factor out a cos2X. :smile:

    hmm … did you mean solve, rather than factor? … then cos2x = 0 is one set of solutions, and the other is … ? :wink:
  4. Nov 11, 2008 #3
    Re: Trig

    You will easy realise it, maybe (not necessarily) if you substitute for cos2X=y, you will come up with y2+y=0. Out of there: y(y+1)=0
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