2cos(Пи-x)меньше либо равно 1
Cos(π-х)≤1/2 π/3+2πn≤π-x≤5π/3+2πn -π+π/3+2πn≤-x≤-π+5π/3+2πn -2π/3+2πn≤-x≤2π/3+2πn -2π/3+2πn≤x≤2π/3+2πn