Sin (pi/5-4x) больше-1/2

Вот 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

- 7π/6 + 2πn < 4x - π/5 < π/6 + 2πn, n∈Z

- 7π/6 + π/5 + 2πn < 4x < π/6 + π/5 + 2πn, n∈Z

- 29π/30 + 2πn < 4x < 11π/30 + 2πn, n∈Z

- 29π/120 + πn/2 < x < 11π/120 + πn/2, n∈Z