Решите неравенство
2cos(2x+П/n)>=1

2cos(2x+π/n)≥1
cos(2x+π/n))≥1/2
-π/3 +2πn≤ 2x+π/n ≤π/3 +2πn; n-celoe
-π/3+2πn-π/n  ≤ 2x  ≤π/3+2πn-π/n
-π/6+πn-π/(2n) ≤x≤ π/6+πn-π/(2n)
-π/6 +π((2n^2 -1)/(2n)) ≤ x≤ π/6+π((2n^2-1)/(2n)); n-celoe

спасибо