2.

[tex]arcsin(tg (\frac{3\pi}{4} )) = arcsin(tg(\pi - \frac{\pi}{4} )) = arcsin( - tg \frac{\pi}{4} ) = \\ = arcsin( - 1) = - \frac{\pi}{2} [/tex]

3.

[tex]tg(arcsin( - \frac{1}{2} )) = tg( - \frac{\pi}{6} ) = - tg( \frac{\pi}{6} ) = - \frac{ \sqrt{3} }{3} [/tex]

4.

не всё видно

[tex]arccos( - 1) - arccos( - \frac{ \sqrt{3} }{2} ) = \pi - \frac{5\pi}{6} = \frac{\pi}{6} [/tex]