Calculate the inverse for arctan(x^2+1)=?iso-8859-1?Q?=2C_x=A1=DD0?=

Calculate the inverse for arctan(x^2+1), x¡Ý0

I have no idea how to solve this problem.
Calculate the inverse for the function: $f(x) = arctan(x^2+1),$ $x¡Ý0$
Also specify $D_{f-1}$ and $V_{f-1}$
I would really appreciate your help