021.18. a) sin (arccos (\(-\frac{1}{2}\))); B) ctg (arccos 0); б) tg (arccos \(\frac{\sqrt{3}}{2}\)); r) sin (arccos \(\frac{\sqrt{2}}{2}\));

a) sin (arccos (\(-\frac{1}{2}\))) = sin (\(\frac{2\pi}{3}\)) = \(\frac{\sqrt{3}}{2}\). б) tg (arccos \(\frac{\sqrt{3}}{2}\)) = tg (\(\frac{\pi}{6}\)) = \(\frac{\sqrt{3}}{3}\). в) ctg (arccos 0) = ctg (\(\frac{\pi}{2}\)) = 0. г) sin (arccos \(\frac{\sqrt{2}}{2}\)) = sin (\(\frac{\pi}{4}\)) = \(\frac{\sqrt{2}}{2}\).