... second group of derivation formulas (Weingarten formulas).The formulas in the second group of derivation formulas express the partial derivatives of the unit normal vector N in terms of the variables ... 2003.Dillen, F. J. E. and Verstraelen, L. C. A., Handbook of Differential Geometry, Vol. 1, North Holland,Amsterdam, 2000.Dillen, F. J. E. and Verstraelen, L. C. A., Handbook of Differential Geometry, ... formulaΓk,ij=12∂gki∂uj+∂gkj∂ui–∂gij∂uk.This is one of the basic formulas in the theory of surfaces; this formula means that thescalar products of the second partial derivatives of the position vector r(ui, uj) by its partialderivatives...