Definition:Prosthaphaeresis/Trigonometry

Definition
The trigonometric technique of prosthapheiresis is based on the Sum-to-Product Formula for Sine plus Sine:
 * $\dfrac {\sin \alpha + \sin \beta} 2 = \sin \left({\dfrac {\alpha + \beta} 2}\right) \cos \left({\dfrac {\alpha - \beta} 2}\right)$