Dear WW: Don't blame me, you started it. The spinning gears in my cranium suddently
meshed again, and printed out "limaçon" a mathematical curve:
The limaçon can be generated by specifying a fixed point P, then drawing a sequences
of circles with centers on a given circle which all pass through P. The envelope of
these curves is a limaçon.
Alas, I struck out trying to find "limaçon" in French dictionary. But since Latin is limax,
I'll bet Pascal use that as source of the name.
If the fixed point is on the circumference of the circle, then the envelope is a cardioid.
The limaçon is an anallagmatic curve, and is also the catacaustic of a circle when the
radiant point is a finite (nonzero) distance from the circumference, as shown by
Thomas de St. Laurent in 1826
(MacTutor Archive). The limaçon is the conchoid of a circle with respect to a point on its
circumference (Wells 1991).
