Help please. Sorry if Im posting several threads. I have an examination tomorrow and need to know how to solve this.

1. $\displaystyle cot [{Arcsec (-2 \sqrt{3/4}) }]$

2. $\displaystyle sin [{arctan (\frac{-5}{12}) }]$

3. $\displaystyle Cos^{-1}[{1/2\sqrt{2} cos[Sin^{-1} (-1) }]$