Jacobi equation in geodesic polar coordinates
= Jacobi equation in geodesic polar coordinates
{title2=$h_{rr}+Kh=0$}
For $h(r,\theta)=\sqrt{G(r,\theta)}$, the angular <Jacobi field> equation on a surface becomes
$$
h_{rr}+K(r,\theta)h=0,
\qquad h(0,\theta)=0,
\qquad h_r(0,\theta)=1.
$$
The <area element of a surface>[Riemannian area element] is $h(r,\theta)\,dr\,d\theta$.