Question

If sina+sin2a+sin3a=1, then find the value of cos6a4cos4a+8cos2a is: a

Answer 1

Answer:

inA + sin2A + sin3A = 1 => sinA + sin3A = 1 - sin2A => sinA ( 1+sin2A ) = cos2A => sinA ( 1 + 1 - cos2A ) = cos2A