3 cos 2 a - 2 sin^2a если sin^2a = 3\4

Question

3 cos 2 a - 2 sin^2a если sin^2a = 3\4

Answer 1

3cos2A - 2sin²A = 3(1 - 2sin²A) - 2sin²A = 3 - 6sin²A - 2sin²A = 3 - 8sin²A = 3 - 8·3/4 = 3 - 6 = -3