Question

Решить неравенство 2cos x>1

Answer 1

2cos x>1              cosx=1/2
cosx>1/2              x=+-(π/3) +2πn, n∈Z
x∈(-(π/3) +2πn; (π/3) +2πn)  или   -(π/3) +2πn<x< (π/3) +2πn
отв: x∈(-(π/3) +2πn; (π/3) +2πn), n∈Z