Question

sin8x=8sinxcosxcos2xcos4x
proving trig identity?

Answer 1

sin 8 x = 2 sin 4x  cos 4x =
= 2 * 2  sin 2x  cos 2x  cos 4 x =
= 4 * 2  sin x  cos x  cos 2x  cos 4x =
= 8  sin x  cos x  cos 2x  cos 4x    ( correct )