Addition formulae for sin(A±B), cos(A±B), tan(A±B). Double angle formulae and their applications.
Fundamental trig identities and using them to simplify expressions and solve equations.
Expressing a sin x + b cos x in the form R sin(x+a) or R cos(x+a). Solving equations and finding maxima/minima.
Constructing proofs of trigonometric identities using known results.