Show that : `cos(2\ tan^(-1)(1/7))=sin(4\ tan^(-1)(1/3))`

Explanation

We have
`\cos (2 \tan ^{-1}(1 / 7))=\sin (4 \tan ^{-1}(1 / 3))`



{ L.H.S. }




`=\cos (2 \tan ^{-1} \frac{1}{7})`



...