Question

Rewrite with only sin x and cos x.

cos 3x

Answer 1

cos(3x)

cos(2x + x)

cos(2x)cos(x) - sin(2x)sin(x)

[cos²(x) - sin²(x)][cos(x)] - [2sin(x)cos(x)][sin(x)]

cos³(x) - sin²(x)cos(x) - 2sin²(x)cos(x)

cos³(x) - 3sin²(x)cos(x)