8. \( \cos 279^\circ, \sin(-\frac{17\pi}{4}), tg 700^\circ, ctg(-\frac{10\pi}{3}) \)

* \( \cos 279^\circ = \cos(270^\circ + 9^\circ) = \sin 9^\circ \) * \( \sin(-\frac{17\pi}{4}) = -\sin(\frac{17\pi}{4}) = -\sin(4\pi + \frac{\pi}{4}) = -\sin(\frac{\pi}{4}) \) * \( tg 700^\circ = tg(360^\circ \cdot 1 + 340^\circ) = tg 340^\circ = tg(360^\circ - 20^\circ) = -tg 20^\circ \) * \( ctg(-\frac{10\pi}{3}) = -ctg(\frac{10\pi}{3}) = -ctg(3\pi + \frac{\pi}{3}) = -ctg(\frac{\pi}{3}) \)