Question

cosa + cos3a + cos5a + cos 70 + cos 9a=sin10a/2sina​

Answer 1

Answer:

Let us consider the LHS sin3A+sin5A+sin7A+sin9Acos3A+cos5A+cos7A+cos9Asin3A+sin5A+sin7A+sin9Acos3A+cos5A+cos7A+cos9A On using the formulas, cos A + cos B = 2cos(A + B)/2 cos(A - B)/2 sin A + sin B = 2 sin(A + B)/2 cos(A - B)/2 Therefore now, = RHSRead more on Sarthaks.com - https://www.sarthaks.com/656167/prove-that-i-sin-3a-sin-5a-sin-7a-sin-9a-cos-3a-cos-5a-cos-7a-cos-9a-tan-6a