SOLUTION: Find an equivalent expression for cos 3x in terms of powers of cos x. cos 3x = cos (2x + x) = cos 2x cos x - sin 2x sin x <----Using cos(u + v) = cos u cos v

SOLUTION: Find an equivalent expression for cos 3x in terms of powers of cos x. cos 3x = cos (2x + x) = cos 2x cos x - sin 2x sin x <----Using cos(u + v) = cos u cos v - s

Question 285156: Find an equivalent expression for cos 3x in terms of powers of cos x.
cos 3x = cos (2x + x)
= cos 2x cos x - sin 2x sin x <----Using cos(u + v) = cos u cos v - sin u sin v
= (cos^2x - sin^2x) cosx - (2 sinx cosx) sinx
= cos^3x -sin^2x cosx - 2sin^2x cosx
I'm stuck up to here....

Answer by eggsarecool(46) (Show Source): You can put this solution on YOUR website!
Going back to this step (cos^2x - sin^2x) cosx - (2 sinx cosx) sinx
You need to use identities
So
Simplify.

And everything is now in terms of powers.
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