Given a curve and a fixed point called the Pedal Point, then for a point on , draw a Line Perpendicular to . The Envelope of these Lines as describes the curve is the negative pedal of .
See also Pedal Curve
References
Lawrence, J. D. A Catalog of Special Plane Curves. New York: Dover, pp. 46-49, 1972.
Lockwood, E. H. ``Negative Pedals.'' Ch. 19 in A Book of Curves. Cambridge, England: Cambridge University Press,
pp. 156-159, 1967.