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