Prove that sin ( n + 1) a sin ( n + 2 )a + cos ( n + 1 - Maths - Trigonometric Functions

Question

Prove that sin ( n + 1) a sin ( n + 2 )a + cos ( n + 1 )a Cos ( n +
2 )a = cos a

Varun.Rawat · Accepted Answer

LHS = sinn+2a sinn+1a + cosn+2a cosn+1a=cosn+2a - n+1a as, cosA-B =
cos A cos B + sin A sin B=cosna+2a-na-a=cos a=RHS

Prove that sin ( n + 1) a.sin ( n + 2 )a + cos ( n + 1 )a. Cos ( n + 2 )a = cos a