|cosx|[tex] \geq \frac{1}{2} [/tex]

[cosx≤-1/2⇒x∈[2π/3+2πn;4π/3+2πn,n∈z][cosx≥1/2⇒x∈[-π/3+2πn;π/3+2πn,n∈z]x∈[-π/3+2πn;π/3+2πn,n∈z] U [2π/3+2πn;4π/3+2πn,n∈z]