Let
I=∫xcos−1(1+x21−x2)dx
\therefore
I=2∫II x
⋅tan−1 x d x
Applying Integration by parts
I=2[tan−1x∫xdx−∫(dxd(tan−1x)∫xdx)dx]I=2[2x2tan−1x−∫1+x21×2x2dx]+cI=2[2x2tan−1x−21∫x2+1x2+1−1dx]+cI=2[2x2tan−1x−21∫x2+1x2+1dx+21∫1+x21dx]+cIII=2[2x2tan−1x−21∫1.dx+21tan−1x]+c=2[2x2tan−1x−2x+21tan−1x]+c=x2tan−1x+tan−1x−x+c or I=−x+(x2+1)tan−1x+c