a) \[ x = \frac{\pi}{6} + 2k\pi, \, x = \frac{5\pi}{6} + 2k\pi \]
b) \[ x = \frac{5\pi}{6} + 2k\pi, \, x = \frac{7\pi}{6} + 2k\pi \]
c) \[ x = \frac{\pi}{4} + k\pi \]
d) \[ x = \frac{k\pi}{2} \]
e) \[ x = \frac{\pi}{4} + 2k\pi, \, x = \frac{3\pi}{4} + 2k\pi, \,\]\[x = \frac{5\pi}{4} + 2k\pi, \, x = \frac{7\pi}{4} + 2k\pi \]
f) \[ x = \frac{\pi}{6} + 2k\pi, \, x = \frac{5\pi}{6} + 2k\pi, \,\]\[x = \frac{7\pi}{6} + 2k\pi, \, x = \frac{11\pi}{6} + 2k\pi \]
