trigpower reducing formulas
posted by Brian .
Having trouble with this problem:
Rewrite the expression as an equivalent expression that does not contain powers greater than 1.
Cos³x
My answer: cos³x=(cos²x)(cosx)
=(1+cos2x/2)(cosx)>cos+cos³x/2...which is wrong

trigpower reducing formulas 
Count Iblis
You have to use doubling formulas again to express it in terms of cos(3x). If you know about complex numbers then the derivation is easy:
cos(x) = [exp(i x) + exp(i x)]/2
cos^3(x) = 1/8 [exp(3 i x) +
exp(3 i x)+ 3 exp(ix) + 3 exp(ix) ] =
1/4 cos(3 x) + 3/4 cos(x) 
trigpower reducing formulas 
sierra
(cosx)+(cosx)(cosx)
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