Задание 3412

а) $x = \pm\frac{\pi}{2} + 2\pi k,\ x = \frac{\pi}{4} + 2\pi k,\ x = \frac{3\pi}{4} + 2\pi k,\ k \in \mathbb{Z}$;

б) $x = -\frac{5\pi}{2},\ x = -\frac{7\pi}{4},\ x = -\frac{3\pi}{2}$.