TrigFactor

TrigFactor[expr] factors trigonometric functions in expr.

Examples

Factor a sum of sines:

TrigFactor[Sin[x] + Sin[y]]
(* 2 Cos[(x - y)/2] Sin[(x + y)/2] *)

Factor a difference:

TrigFactor[Cos[x] - Cos[y]]
(* -2 Sin[(x - y)/2] Sin[(x + y)/2] *)

Please visit the official Wolfram Language Reference for more details.