Miklos Schweitzer 1965_6
Source:
September 25, 2008
advanced fieldsadvanced fields unsolved
Problem Statement
Consider the radii of normal curvature of a surface at one of its points in two conjugate direction (with respect to the Dupin indicatrix). Show that their sum does not depend on the choice of the conjugate directions. (We exclude the choice of asymptotic directions in the case of a hyperbolic point.)