Задание 4907

а) $\frac{\pi}{2}+\pi n,\ -\frac{\pi}{6}+2\pi n,\ -\frac{5\pi}{6}+2\pi n,\ n\in\mathbb{Z}$

б) $\frac{7\pi}{2};\ \frac{23\pi}{6};\ \frac{9\pi}{2}$