1. Вычислите: a) \( \sin \frac{9\pi}{4} \) b) \( \cos(-\frac{4\pi}{3}) \) c) \( tg(-\frac{7\pi}{6}) \) d) \( ctg\frac{5\pi}{4} \)

a) \( \sin \frac{9\pi}{4} = \sin (2\pi + \frac{\pi}{4}) = \sin \frac{\pi}{4} = \frac{\sqrt{2}}{2} \) б) \( \cos(-\frac{4\pi}{3}) = \cos(\frac{4\pi}{3}) = \cos(\pi + \frac{\pi}{3}) = -\cos(\frac{\pi}{3}) = -\frac{1}{2} \) в) \( tg(-\frac{7\pi}{6}) = -tg(\frac{7\pi}{6}) = -tg(\pi + \frac{\pi}{6}) = -tg(\frac{\pi}{6}) = -\frac{\sqrt{3}}{3} \) г) \( ctg(\frac{5\pi}{4}) = ctg(\pi + \frac{\pi}{4}) = ctg(\frac{\pi}{4}) = 1 \)