Problem
Problem 6.74 Find the Riemann-Christoffel curvature tensor of the Riemannian manifold $(U, g)$, where $U$ denotes the unit open disk of the plane $\mathbb{R}^{2}$ and
$$
g=\frac{1}{1-x^{2}-y^{2}}\left(\mathrm{~d} x^{2}+\mathrm{d} y^{2}\right)
$$