Epispiral

The epispiral is a plane curve with polar equation

$\ r=a \sec{n\theta}$ .

There are n sections if n is odd and 2n if n is even.

It is the polar or circle inversion of the rose curve.

References

J. Dennis Lawrence (1972). A catalog of special plane curves. Dover Publications. p. 192. ISBN 0-486-60288-5.