What is ^ -1 ((1)/(4))+ ^ -1 ((3)/(5))equal to?

$\tan ^{-1}\left(\frac{1}{4}\right)+\tan ^{-1}$\left(\frac{3}{5}\right)$We know,$\tan ^{-1} x+\tan ^{-1} y=\tan ^{-1}\left(\frac{x+y}{1-x y}\right)$So,$\tan ^{-1}\left(\frac{1}{4}\right)+\tan ^{-1}\left(\frac{3}{5}\right)=\tan ^{-1}\left(\frac{\frac{1}{4}+\frac{3}{5}}{1-\left(\frac{1}{4}\right)\left(\frac{3}{5}\right)}\right)$$\begin{aligned} & =\tan ^{-1}\left(\frac{\frac{5+12}{20}}{1-\frac{3}{20}}\right) \\ & =\tan ^{-1}\left(\frac{\frac{17}{20}}{\frac{17}{20}}\right)=\tan ^{-1}(1)=\frac{\pi}{4} \end{aligned}$$