Question:
Mark $(\sqrt{)}$ against the correct answer in the following:
If $y=\sec ^{-1}\left(\frac{x^{2}+1}{x^{2}-1}\right)$ then $\frac{d y}{d x}=?$
A. $\frac{-2}{\left(1+x^{2}\right)}$
B. $\frac{2}{\left(1+x^{2}\right)}$
C. $\frac{-1}{\left(1+\mathrm{x}^{2}\right)}$
D. none of these
Solution:
