Sectional curvature
= Sectional curvature
{title2=$K(\sigma)$}
{wiki}
For a two-plane $\sigma=\operatorname{span}(X,Y)$ in a Riemannian tangent space,
$$
K(\sigma)=\frac{\langle R(X,Y)Y,X\rangle}{|X|^2|Y|^2-\langle X,Y\rangle^2}.
$$
= Sectional curvature
{title2=$K(\sigma)$}
{wiki}
For a two-plane $\sigma=\operatorname{span}(X,Y)$ in a Riemannian tangent space,
$$
K(\sigma)=\frac{\langle R(X,Y)Y,X\rangle}{|X|^2|Y|^2-\langle X,Y\rangle^2}.
$$