If $\sin \left(\sin ^{-1} \frac{1}{5}+\cos ^{-1} x\right)=1$,then the value of $x$ is

The real value of $x$ that satisfies the equation $\tan ^{-1} x+\tan ^{-1} 2 x=\frac{\pi}{4}$ is

If $\tan ^{-1}\left(\frac{x}{2}\right)+\tan ^{-1}\left(\frac{y}{2}\right)+\tan ^{-1}\left(\frac{z}{2}\right)=\frac{\pi}{2}$,then $x y+y z+z x=$

$\lim _{x \rightarrow 0^{+}} \frac{x \sin ^{-1}\left(\frac{2 x}{1+x^2}\right)}{\cos ^{-1}\left(\frac{1-x^2}{1+x^2}\right) \tan ^{-1}\left(\frac{3 x-x^3}{1-3 x^2}\right)}$ is equal to

$\frac{d}{dx} \sin^{-1}(3x - 4x^3)$ is equal to

$\sin^{-1} \frac{1}{\sqrt{5}} + \cot^{-1} 3$ is equal to