6. \( \cos 365^\circ, \sin(-\frac{13\pi}{4}), tg(-451^\circ), ctg(-\frac{7\pi}{5}) \)

* \( \cos 365^\circ = \cos(360^\circ + 5^\circ) = \cos 5^\circ \) * \( \sin(-\frac{13\pi}{4}) = -\sin(\frac{13\pi}{4}) = -\sin(3\pi + \frac{\pi}{4}) = \sin(\frac{\pi}{4}) \) * \( tg(-451^\circ) = -tg 451^\circ = -tg(360^\circ + 91^\circ) = -tg 91^\circ = -tg(90^\circ + 1^\circ) = ctg 1^\circ \) * \( ctg(-\frac{7\pi}{5}) = -ctg(\frac{7\pi}{5}) = -ctg(\pi + \frac{2\pi}{5}) = -ctg(\frac{2\pi}{5}) \)