Let

$\displaystyle F(x) = \int_{1}^{x}{(1+t^2)^{\frac{1}{2}}dt}$ , $\displaystyle 1 \le x$ . Let G be the inverse function of F. Evaluate G'(0).

I have $\displaystyle F'(x)=(1+x^2)^{\frac{1}{2}}$ for $\displaystyle 1 \le x$ but I am having trouble finding G(x)