Вариант II 1. Вычислите: a) $$\cos(-210^{\circ})$$; б) $$\operatorname{tg} \frac{4\pi}{3}$$; в) $$2\sin \frac{\pi}{2} - \operatorname{tg} \frac{\pi}{3}$$

a) $$\cos(-210^{\circ}) = \cos(210^{\circ}) = \cos(180^{\circ} + 30^{\circ}) = -\cos(30^{\circ}) = -\frac{\sqrt{3}}{2}$$. б) $$\operatorname{tg} \frac{4\pi}{3} = \operatorname{tg}(\pi + \frac{\pi}{3}) = \operatorname{tg} \frac{\pi}{3} = \sqrt{3}$$. в) $$2\sin \frac{\pi}{2} - \operatorname{tg} \frac{\pi}{3} = 2 \cdot 1 - \sqrt{3} = 2 - \sqrt{3}$$. Ответ: a) $$-\frac{\sqrt{3}}{2}$$; б) $$\sqrt{3}$$; в) $$2 - \sqrt{3}$$