Вычислите cos(38π/3). Выберите один ответ: √2/2 √3/2 -1/2 -√3/2

Question

Вычислите cos(38π/3).
Выберите один ответ:
√2/2
√3/2
-1/2
-√3/2

Answer 1

Cos(38π/3)=cos(36π/3+2π/3)=cos(12π+2π/3)=
=cos(6.2π+2π/3)=cos(2π/3)=-cos(π/3)=-1/2
Otvet: -1/2

(cos(α+2π)=cosα)