View source for Base of a deformation

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A [[Conjugate net|conjugate net]] on a surface $F$ and its deformation $F^*$ outside their points of congruence. The base of a deformation is characterized by the fact that the bend — the relation between the normal curvatures $k$ and $k^*$ at isometrically-corresponding points of $F$ and $F^*$ along corresponding directions — has extremal values along the directions of the base of the deformation.

====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  V.F. Kagan,   "Foundations of the theory of surfaces in a tensor setting" , '''2''' , Moscow-Leningrad  (1948)  (In Russian)</TD></TR></table>



====Comments====
For more references on the topic of deforming or bending surfaces, cf. the article [[Deformation, isometric|Deformation, isometric]].