1) sinα = - 3/8;  sin²α = 9/64;  cos²α = 1 - 9/64 = 55/64 ⇒ 5 - 6 cos2α =

5 - 6 · (cos²α - sin²α) = 5 - 6 · (55/64 - 9/64) = 5 - 6 · 46/64 =

5 - (3 · 46) : 32 = 22/32 = 11/16