Prove the following:
(i) $\left(\cot ^{-1}\right)^{\prime} y=-\frac{1}{1+y^{2}}$ for all $y \in \mathbb{R}$,
(ii) $\left(\mathrm{csc}^{-1}\right)^{\prime} y=-\frac{1}{|y| \sqrt{y^{2}-1}}$ for all $y \in \mathbb{R}$ with $|y|>1$,
(iii) $\left(\mathrm{sec}^{-1}\right)^{\prime} y=\frac{1}{|y| \sqrt{y^{2}-1}}$ for all $y \in \mathbb{R}$ with $|y|>1$.