Verified answer

Решение

Упростим левую часть

cosx*cos60 - sinx*sin60 = cos(x + 60°)

Упростим правую часть

sin200*cos25 + cos200*sin25 = sin(200° + 25°) = sin(180° + 45°) =

= - sin(45°) = -  √2/2

Решим уравнение:

cos(x +π/3) = - √2/2

x + π/3 = ±arccos(- √2/2) + 2πn, n∈Z

x + π/3 = ±( π- π/4) + 2πn, n∈Z

x =  ±(3π/4) - π/3 + 2πn, n∈Z