Question

сos2x<1/2
тригономеорическое неравенство

Answer 1

cos2x<1/2
π/3+2πn<2x<5π/3+2πn
π/6+πn<x<5π/6+πn,n∈z
x∈(π/6+πn;5π/6+πn,n∈z)