CARDIOIDE

, the name of a curve so called by Castilliani.—But it was first treated of by Koersma, and by Carré. See Philos. Trans. 1741, and Memoires de l'Acad. 1705.

The Cardioide is thus generated. APB is a circle, and AB its diameter. Through one extremity A of the diameter draw a number of lines APQ, cutting the circle in P; upon these set off always PQ equal to the diameter AB; so shall the points Q be always in the curve of the cardioide.

From this generation of the curve, its chief properties are evident, viz, that,

everywhere PQ = AB,