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(Nevermind) Establish Trig Identity: Sums to Products

  1. Oct 7, 2011 #1
    1. The problem statement, all variables and given/known data
    Establish the identity: 1+cos(2θ)+cos(4θ)+cos(6θ)=4cosθcos(2θ)cos(3θ)


    2. Relevant equations
    cos(a)+cos(b)=2cos((a+b)/2)cos((a-b)/2)


    3. The attempt at a solution
    I understand how to do a simple cos(+/-)cos problem according to the Sums as Products equations, but I am confused on how to handle adding 3 cosine functions plus 1.

    EDIT: cos(0)=1, so I split the problem into 2 additions problems, cos(0θ)+cos(2θ) and cos(4θ)+cos(6θ).
     
    Last edited: Oct 7, 2011
  2. jcsd
  3. Oct 19, 2011 #2
    So you figured it out already?
     
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