Conchoid of de Sluze (Cartesian coordinates)
The conchoid(s) of de Sluze is a family of plane curves. In Cartesian coordinates, the curves satisfy an implicit equation. They are rational, circular, cubic plane curves. Their shape is depending on the value of the parameter a . Except that for a=0 the implicit form has an acnode (0,0) . (An acnode is an isolated point not on a curve, but whose coordinates satisfy the equation of the curve).