Cartesian parametrization:  . Cartesian equation: . Rational sextic.

The rotation of this curve around Oz combined with a scaling of factor 1/2 in the direction Oz yields a flying saucer. Parametrization:
The image by a dilatation of rapport 1/2 is very close to the inverse of the nephroid, that has the parametrization : .	Nephroid (in blue) and its inverse (in red)

See also the mouth and the heart.
 

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© Robert FERRÉOL 2020