The derivative of $\cos ^{-1}\left(2 x^{2}-1\right)$ with respect to $\cos ^{-1} x$ is

If for $x \in \left(0, \frac{1}{4}\right)$,the derivative of $\tan^{-1}\left(\frac{6x\sqrt{x}}{1-9x^3}\right)$ is $\sqrt{x} \cdot g(x)$,then $g(x)$ equals

The value of $\cos ^{-1}\left\{\frac{1}{\sqrt{2}}\left(\cos \frac{9 \pi}{10}-\sin \frac{9 \pi}{10}\right)\right\}$ is

If $\cos^{-1} x - \cos^{-1} \frac{y}{2} = \alpha$,then $4x^2 - 4xy \cos \alpha + y^2$ is equal to

If $0 < x < 1$ and $\tan ^{-1}(1-x), \tan ^{-1} x$ and $\tan ^{-1}(1+x)$ are in $A$.$P$.,then $x^3$ is equal to : . . . . . . .

The value of $\cot \left( {\sum\limits_{n = 1}^{19} {{{\cot }^{ - 1}}\left( {1 + \sum\limits_{p = 1}^n {2p} } \right)} } \right)$ is