Maths唔識抵死題(QUICK)

Prove the following:

a) (Sin x + sin 2x) / (1 + cos x + cos 2x ) = tan x

b) Cos 3A = 4 cos^3 A - 3cos A

c) Tan 3A = 3 tan A - tan^3 A / 1- 3 tan^2 A