Cos2d+2sin(d+30°)•sin (d-30°)

Question

Cos2d+2sin(d+30°)•sin (d-30°)

Answer 1

Cos2d + 2* 1/2 * (cos 60° -cos2d)
Cos2d + (1/2-cos2d)
Cos2d + 1/2 - cos2d
Ответ: 1/2