1. Вычислите: a) sin 3; (-) 50 (9 r) ctg 13,5%.

Решение:

1. $$sin \frac{7\pi}{3} = sin (2\pi + \frac{\pi}{3}) = sin \frac{\pi}{3} = \frac{\sqrt{3}}{2}$$
2. $$tg(-\frac{13\pi}{6}) = -tg(\frac{13\pi}{6}) = -tg(2\pi + \frac{\pi}{6}) = -tg(\frac{\pi}{6}) = -\frac{\sqrt{3}}{3}$$
3. $$cos(-\frac{5\pi}{4}) = cos(\frac{5\pi}{4}) = cos(\pi + \frac{\pi}{4}) = -cos(\frac{\pi}{4}) = -\frac{\sqrt{2}}{2}$$
4. $$ctg(13.5\pi) = ctg(13\pi + \frac{\pi}{2}) = ctg(\frac{\pi}{2}) = 0$$

Ответ: a) $$\frac{\sqrt{3}}{2}$$; б) $$\frac{-\sqrt{3}}{3}$$; в) $$\frac{-\sqrt{2}}{2}$$; г) 0