Question

rewrite with only sin x and cos x. cos 3x

Answer 1

you can rewrite it:

\(\cos(3x) = \cos(2x+x)\)

Answer 2

then you use sum formula

Answer 3

yeah, i got it to cos\[\cos 2x(\cos x- \sin 2x \sin x)\]

Answer 4

now do same with cos 2x and sin 2x:

\(\cos (2x) = \cos(x+x)\)