16. \( \sin 312^\circ, \cos(-\frac{15\pi}{9}), tg(-424^\circ), ctg(\frac{12\pi}{5}) \)

* \( \sin 312^\circ = \sin(360^\circ - 48^\circ) = -\sin 48^\circ \) * \( \cos(-\frac{15\pi}{9}) = \cos(-\frac{5\pi}{3}) = \cos(\frac{5\pi}{3}) = \cos(2\pi - \frac{\pi}{3}) = \cos(\frac{\pi}{3}) \) * \( tg(-424^\circ) = -tg 424^\circ = -tg(360^\circ + 64^\circ) = -tg 64^\circ \) * \( ctg(\frac{12\pi}{5}) = ctg(2\pi + \frac{2\pi}{5}) = ctg(\frac{2\pi}{5}) \)