a) sin300° = sin(360° - 60°) = -sin60° = -$$\frac{\sqrt{3}}{2}$$.
б) tg(-$$\frac{2\pi}{3}$$) = -tg($$\frac{2\pi}{3}$$) = -tg(120°) = -(-$$\sqrt{3}$$) = $$\sqrt{3}$$.
в) 2sin$$\frac{\pi}{3}$$ - cos$$\frac{\pi}{2}$$ = 2 * $$\frac{\sqrt{3}}{2}$$ - 0 = $$\sqrt{3}$$.