Trigonometry

Trigonometric identities of double angles

Keywords: trigonometric identities of double angles

s i n 2 α = 2 s i n α · c o s α = 2 t g α 1 + t g 2 α
c o s 2 α = c o s 2 α s i n 2 α = 1 t g 2 α 1 + t g 2 α
t g 2 α = 2 t g α 1 t g 2 α
c t g 2 α = c t g 2 α 1 2 c t g α