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Principal Curvatures


The maximum and minimum of the normal curvature kappa_1 and kappa_2 at a given point on a surface are called the principal curvatures. The principal curvatures measure the maximum and minimum bending of a regular surface at each point. The Gaussian curvature K and mean curvature H are related to kappa_1 and kappa_2 by

K=kappa_1kappa_2
(1)
H=1/2(kappa_1+kappa_2).
(2)

This can be written as a quadratic equation

 kappa^2-2Hkappa+K=0,
(3)

which has solutions

kappa_1=H+sqrt(H^2-K)
(4)
kappa_2=H-sqrt(H^2-K).
(5)

See also

Gaussian Curvature, Mean Curvature, Normal Curvature, Normal Section, Principal Direction, Principal Radius of Curvature, Rodrigues' Curvature Formula

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References

Geometry Center. "Principal Curvatures." http://www.geom.umn.edu/zoo/diffgeom/surfspace/concepts/curvatures/prin-curv.html.Gray, A. "Normal Curvature." §16.2 in Modern Differential Geometry of Curves and Surfaces with Mathematica, 2nd ed. Boca Raton, FL: CRC Press, pp. 363-367, 376, and 378, 1997.

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Principal Curvatures

Cite this as:

Weisstein, Eric W. "Principal Curvatures." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/PrincipalCurvatures.html

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