Question

|cosx|$geq frac{1}{2}$

Answer 1

[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]