Curves95 of 113
Cardioid
Ole Rømer, 1674; named by Castillon, 1741
Roll a circle round another of the same size and a point on its rim draws a cardioid, the epicycloid with one cusp. Number points around a circle and join each point n to point 2n: the chords outline a cardioid. A cardioid makes the main body of the Mandelbrot set.
r = 2a(1 + cos φ)
On mathcurve.com as Cardioïde