Hippopede

$\begin{figure}\begin{center}\BoxedEPSF{hippopede.epsf}\end{center}\end{figure}$

A curve also known as a Horse Fetter and given by the polar equation

$\begin{displaymath} r^2=4b(a-b\sin^2\theta). \end{displaymath}$

References

Lawrence, J. D. A Catalog of Special Plane Curves. New York: Dover, pp. 144-146, 1972.