The folium 2 has three forms:
Each of the three folia is a (different) pedal of
It was Johann Kepler (1609) who was the first to describe the curve.
Therefore the curve is also known as Kepler's folium.
1) In Cartesian coordinates: (x2 + y2)2 + a
x3 = (1-a) x y2
2) Folium (Lat.) = leaf.
3) In French: oreilles de lapin.
4) To be distinguished from the cubic trefoil.
5) In French: torpille.