1) 2Cos53°/Sin37° + 13 = 2Sin37°/Sin37° +13 = 2 + 13 = 15
2)Числитель = -21(Cos²66° - Sin66°) = -21*Cos132°
Ответ: -21
3) 12Sin150°*Cos120° = -12Sin30°*Cos60° = -12*1/2*1/2= -3
Пояснение: Sin150° = Sin(180°-30°) = Sin30° =1/2;
Сos120° = Cos(180° -60°) = - Cos60° = -1/2
4) = 1 - Сosα*Cosα - Sin²α = 1 - Cos²α -Sin²α = Sin²α - Sin²α = 0