∫116tan−1x−1dx=
8π3+3
8π3−3
16π3−23
16π3+23
x−1=t2,x=(t2+1)2
I=∫03tan−1t d(t2+1)2 =tan−1t⋅(t2+1)2|03−∫03(t2+1)dt by parts
=16π3−(t33+t)03=16π3−23