1. Вычислить: 1) cos 765°; 2) sin$$\frac{19\pi}{6}$$.

1) cos 765° = cos (720° + 45°) = cos (2 * 360° + 45°) = cos 45° = $$\frac{\sqrt{2}}{2}$$. 2) sin$$\frac{19\pi}{6}$$ = sin($$\frac{18\pi + \pi}{6}$$) = sin(3$$\pi + \frac{\pi}{6}$$) = sin(2$$\pi + \pi + \frac{\pi}{6}$$) = sin($$\pi + \frac{\pi}{6}$$) = -sin($$\frac{\pi}{6}$$) = -$$\frac{1}{2}$$. Ответ: 1) $$\frac{\sqrt{2}}{2}$$; 2) -$$\frac{1}{2}$$.