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Homework Help: (Trig) Rewriting using power-reducing formula?

  1. Oct 10, 2011 #1
    1. The problem statement, all variables and given/known data
    Rewrite sin^4 xtan^4 x in terms of the 1st power of the cosine.

    2. Relevant equations
    sin^2 x=(1-cosx)/2
    tan^2 x=(1-cosx)/(1+cosx)

    3. The attempt at a solution

    For this problem, I tried to rewrite tan^2 x as (sin^2 x/cos^2 x)
    But then I ended up with a...cubic function, which made the problem even more complicated. What am I doing wrong here?
  2. jcsd
  3. Oct 11, 2011 #2


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    The problem you posted was sin4(x) tan4(x). -- both with the power, 4.

    Your answer still has cos3 & cos2 .


    = (1-cos2(x))sin2(x)

    = sin2(x) - cos2(x)sin2(x)

    = (1 - cos(2x))/2 - sin2(2x)/4

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