Curvatures of an arc-length surface of revolution (source code)

= Curvatures of an arc-length surface of revolution

With unit normal $(-Z'\cos v,-Z'\sin v,Y')$, the principal-form coefficients give
$$
K=-\frac{Y''}{Y},
\qquad
H=\frac12\left(Y'Z''-Z'Y''+\frac{Z'}Y\right).
$$