The word ``folium'' means leaf-shaped. The polar equation is

If , it is a single folium. If , it is a Bifolium. If , it is a Trifolium. The simple folium is the Pedal Curve of the Deltoid where the Pedal Point is one of the Cusps.

**References**

Lawrence, J. D. *A Catalog of Special Plane Curves.* New York: Dover, pp. 152-153, 1972.

MacTutor History of Mathematics Archive. ``Folium.'' http://www-groups.dcs.st-and.ac.uk/~history/Curves/Folium.html.

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1999-05-26