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$$\begin{gathered} \mathrm{Q}. \mathrm{Find} \frac{\mathrm{dy}}{\mathrm{dx}} \mathrm{when}: \\ \left(\mathrm{viii}\right) \mathrm{y}= {\tan }^{-1}\left[\sqrt{\frac{\mathrm{a}-\mathrm{b}}{\mathrm{a}+\mathrm{b}}} \tan \frac{\mathrm{x}}{2}\right] \\ \mathrm{Ans}: \frac{\sqrt{{\mathrm{a}}^2-{\mathrm{b}}^2}}{2\left(\mathrm{a}+\mathrm{b} \cos \mathrm{x}\right)} \end{gathered}$$