Double angle equations are allowing the expression of trigonometric functions of angles equal to 2u in terms of u.
The double angle formulas can simplify the functions and gives ease to perform more complex calculations. The double angle formulas are useful for finding the values of unknown trigonometric functions. Therefore in double angle equation we need to consider two rotation. Due to two rotation it give double angles of given values. Therefore all double angle equation are as follows.
sin2θ = 2sinθcosθ
cos2θ = cos²θ − sin²θ
