If $f(x) = 2 \tan^{-1} x + \sin^{-1} \left( \frac{2x}{1 + x^2} \right)$,where $x > 1$,then $f(5)$ is equal to:

If $\tan^{-1} \frac{a+x}{a} + \tan^{-1} \frac{a-x}{a} = \frac{\pi}{6}$,then $x^2 =$

Prove $3 \cos ^{-1} x = \cos ^{-1} (4 x^{3} - 3 x)$,where $x \in [\frac{1}{2}, 1]$.

If $ a + \frac{\pi}{2} < 2 \tan^{-1} x + 3 \cot^{-1} x < b $,then find the values of $ a $ and $ b $.

Let the maximum value of $(\sin^{-1}x)^{2} + (\cos^{-1}x)^{2}$ for $x \in [-\frac{\sqrt{3}}{2}, \frac{1}{\sqrt{2}}]$ be $\frac{m}{n}\pi^{2}$, where $\gcd(m, n) = 1$. Then $m+n$ is equal to ........... .

If $\frac{\pi}{2} \leq x \leq \frac{3 \pi}{4}$,then $\cos ^{-1}\left(\frac{12}{13} \cos x+\frac{5}{13} \sin x\right)$ is equal to