Question

Срочно ! Помогите пожалуйста

Answer 1

1.  cos125° = cos(180° – 55°) = - cos 55°

2.  sin 5π/6 = sin (π – π/6)  = sin π/6

3.  sin 70° = sin(90° – 20°) = cos 20°

4.  cos π/3 = cos(π/2 – π/6) = sin π/6

cos 2π/3 = cos (π – π/3) = - cos π/3 = - 1/2

cos 5π/6 = cos (π – π/6) = - cos π/6 = - $frac{ sqrt{3} }{2}$