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PEDAL OF A SURFACE OR A CURVE

The *pedal* (*surface*) of a surface or a curve with respect to a point *O* is the locus of the feet of the lines passing by *O* perpendicular to the tangent planes of the surface or the osculating planes of the curve .

In the case of a surface, the pedal is the envelope of the spheres with diameter [*OM** _{0}*], when

In the case of a curve, the pedal is the circled surface composed of the circles with diameter [*OM** _{0}*],
perpendicular to the tangent to the curve at

Example: the pedal of the ellipsoid with respect to its center is Fresnel's elasticity surface.

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© Robert FERRÉOL
2017