3. \( \sin(-305^\circ), \cos(-\frac{15\pi}{8}), tg 392^\circ, ctg(-\frac{17\pi}{6}) \)

* \( \sin(-305^\circ) = -\sin 305^\circ = -\sin (360^\circ - 55^\circ) = \sin 55^\circ \) * \( \cos(-\frac{15\pi}{8}) = \cos(\frac{15\pi}{8}) = \cos(2\pi - \frac{\pi}{8}) = \cos(\frac{\pi}{8}) \) * \( tg 392^\circ = tg(360^\circ + 32^\circ) = tg 32^\circ \) * \( ctg(-\frac{17\pi}{6}) = -ctg(\frac{17\pi}{6}) = -ctg(2\pi + \frac{5\pi}{6}) = -ctg(\frac{5\pi}{6}) = -ctg(\pi - \frac{\pi}{6}) = ctg(\frac{\pi}{6}) \)