Решите уравнения: (1+2cosx)(1-3cosx)=0

(1+2cosx)(1-3cosx)=0
1+2cosx=0 или 1-3cosx=0
1. 1+2cosx=0
2cosx=-1
cosx=-1/2
x=+-(π-π/3)+2πn, n∈Z
x=+-(2π/3)+2πn, n∈Z
2. 1-3cosx=0
3cosx=1
cosx=1/3
x=+-arccos1/3+2πn, n∈Z