Rumus trigonometri sudut rangkap yang sering digunakan:
\(\sin 2x = 2 \sin x \cos x\)
\(\cos 2x = 2 \cos^2 x - 1\)
\(\cos 2x = 1 - 2 \sin^2 x\)
\(\tan 2x = \dfrac {2 \tan x}{1 - \tan^2 x}\)
\(\sin 3x = 3 \sin x - 4 \sin^3 x\)
\(\cos 3x = 4 \cos^3 x - 3 \cos x\)