half-angle identities | trigonometric half-angle identities

A set of formulas that express trigonometric functions of half an angle in terms of the trigonometric functions of the original angle.

Half-angle formulas and formulas expressing trigonometric functions of an angle x/2 in terms of functions of an angle x. For real x,

double-angle formulas | hyperbolic functions | multiple-angle formulas | prosthaphaeresis formulas | trigonometric addition formulas | trigonometric functions | trigonometry | Weierstrass substitution

high school level (California trigonometry standard)