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Homework Help: Expressing cos^6(x)?

  1. Oct 12, 2011 #1
    1. The problem statement, all variables and given/known data
    Express cos^6(x) in a form that does not involve powers of trig functions


    2. Relevant equations

    idk actually........binomial theorem? algebra? lol


    3. The attempt at a solution

    ok, so i realized that it can be expressed as (cos^2(x))^3

    and that can be ((cos(2x) + 1)/2)^3

    and that can be expanded as

    1/8+3/8 cos(2 x)+3/8 cos^2(2 x)+1/8 cos^3(2 x)

    but how do i get the answer with no powers in in? idk what to do up until that point
     
  2. jcsd
  3. Oct 12, 2011 #2

    SammyS

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    You already showed how to handle cos2(x). Do a similar thing with cos2(2x).
     
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