10. \( \cos 284^\circ, \sin(-\frac{16\pi}{7}), tg(-451^\circ), ctg(\frac{17\pi}{6}) \)

* \( \cos 284^\circ = \cos(270^\circ + 14^\circ) = \sin 14^\circ \) * \( \sin(-\frac{16\pi}{7}) = -\sin(\frac{16\pi}{7}) = -\sin(2\pi + \frac{2\pi}{7}) = -\sin(\frac{2\pi}{7}) \) * \( tg(-451^\circ) = -tg 451^\circ = -tg(360^\circ + 91^\circ) = -tg 91^\circ = -tg(90^\circ + 1^\circ) = ctg 1^\circ \) * \( ctg(\frac{17\pi}{6}) = ctg(2\pi + \frac{5\pi}{6}) = ctg(\frac{5\pi}{6}) = ctg(\pi - \frac{\pi}{6}) = -ctg(\frac{\pi}{6}) \)