Решить уравнение cos(3x+pi/(4))=-sqrt(3)/(2)

Cos(3x + π/4) = -√3/2
3x + π/4 = ±5π/6 + 2πn, n ∈ Z
3x = ±5π/6 - π/4 + 2πn, n ∈ Z
x = ±5π/18 - π/12 + 2πn/3, n ∈ Z
ответ: x = ±5π/18 - π/12 + 2πn/3, n ∈ Z.