A cardioid is a plane curve traced by a point on the perimeter of a circle that is rolling around a fixed circle of the same radius.
It is therefore a type of limaçon
and can also be defined as an epicycloid
having a single cusp. It is also a type of sinusoidal spiral
, and an inverse curve of the parabola
with the focus as the center of inversion.
The name cardioid
, which means heart-shaped, was introduced by Giovanni Salvemini
called Castiglione (or even Johann Castillon) in an article written in Latin and published in the Philosophical Transactions of the Royal Society
, in 1741. However, in the study of that curve, he had been preceded already, in 1708, by Philippe de La Hire
, who had determined its length.
► Animation source>>http://flotsam.sellingwaves.com/post/127530671911/spinning-in-place-loosely-inspired-by Further reading
, from +Xah Lee #cardioid