Pedal Coordinates

The pedal coordinates of a point $P$ with respect to the curve $C$ and the Pedal Point $O$ are the radial distant $r$ from $O$ to $P$ and the Perpendicular distance $p$ from $O$ to the line $L$ tangent to $C$ at $P$.

References

Lawrence, J. D. A Catalog of Special Plane Curves. New York: Dover, pp. 2-3, 1972.

Yates, R. C. ``Pedal Equations.'' A Handbook on Curves and Their Properties. Ann Arbor, MI: J. W. Edwards, pp. 166-169, 1952.