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Orthoptic Curve

An Isoptic Curve formed from the locus of Tangents meeting at Right Angles. The orthoptic of a Parabola is its Directrix. The orthoptic of a central Conic was investigated by Monge and is a Circle concentric with the Conic Section. The orthoptic of an Astroid is a Circle.

Curve Orthoptic
Astroid Quadrifolium
Cardioid Circle or Limaçon
Deltoid Circle
Logarithmic Spiral equal Logarithmic Spiral
Parabola Directrix


Lawrence, J. D. A Catalog of Special Plane Curves. New York: Dover, pp. 58 and 207, 1972.

© 1996-9 Eric W. Weisstein