Answer:
sin x * sin x = 1/2 (cos (x-x) - cos (x+x)) = 1/2 (cos (0) - cos (2x))
Step-by-step explanation:
sin² x = sin x * sin x
using the product-to-sum identity for sine
sin x * sin x = 1/2 (cos (x-x) - cos (x+x)) = 1/2 (cos (0) - cos (2x))
cos (0) = 1
sin² x = (1 - cos (2x)) /2
