Lawrence (1972) defines a trifolium as a Folium with . However, the term ``the'' trifolium is
sometimes applied to the Folium with , which is then the 3-petalled Rose with Cartesian equation

and polar equation

The trifolium with is the Radial Curve of the Deltoid.

**References**

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

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

© 1996-9

1999-05-26