Question

Rewrite with only sin x and cos x.

cos 3x

Answer 1

cos x - 4 cos x sin^2x

-sin^3x + 2 sin x cos x

-sin^2x + 2 sin x cos x

2 sin^2x cos x - 2 sin x cos x

Answer 2

\[\cos(3x) = \cos(2x+x)\]
\[=\cos(2x)\cos x - \sin(2x)\sin x\]
\[=(1-2\sin^{2}x)\cos x - 2\sin^{2} x \cos x\]
\[\cos x - 4\sin^{2}x \cos x\]

Answer 3

Thats what i got too but its not one of the answer choices so im confused...?

Answer 4

look at option 1 :)

Answer 5

oh its just in a different order... oops :p thanks @dumbcow