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Trifolium

\begin{figure}\begin{center}\BoxedEPSF{Trifolium.epsf scaled 700}\end{center}\end{figure}

Lawrence (1972) defines a trifolium as a Folium with $b\in (0,4a)$. However, the term ``the'' trifolium is sometimes applied to the Folium with $b=a$, which is then the 3-petalled Rose with Cartesian equation

\begin{displaymath}
(x^2+y^2)[y^2+x(x+a)]=4axy^2
\end{displaymath}

and polar equation

\begin{displaymath}
r=a\cos\theta(4\sin^2\theta-1)=-a\cos(3\theta).
\end{displaymath}

The trifolium with $b=a$ is the Radial Curve of the Deltoid.

See also Bifolium, Folium, Quadrifolium


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 Eric W. Weisstein
1999-05-26