Question

Rewrite with only sin(x) and cos(x).

sin(3x)

Answer 1

sin 3x = sin (2x + x)

= sin2x cos x + cos 2x sin x (using the compound angle identity)

= 2sin x cos x.cos x (1 - 2sin^2x) sinx (using identities for sin2x and cos2x)

= 2 sin cos^2 x + sin x - 2 sin^3 x