Решение
sin (П/5-4x) > -1/2
sin(4x - π/5) < 1/2
- π - arcsin(1/2) + 2πn < 4x - π/5 < arcsin(1/2) + 2πn, n∈z
- π - π/6 + 2πn < 4x - π/5 < π/6 + 2πn, n∈Z<br> - 7π/6 + 2πn < 4x - π/5 < π/6 + 2πn, n∈Z<br> - 7π/6 + π/5 + 2πn < 4x < π/6 + π/5 + 2πn, n∈Z<br> - 29π/30 + 2πn < 4x < 11π/30 + 2πn, n∈Z
- 29π/120 + πn/2 < x < 11π/120 + πn/2, n∈Z