Andrew Harper

A cardioid in a limaçon in a limaçon--because where else would it have got its name from? Well, it could have got its name from limes and lemons...but no. However, there are at least four lenses which shouldn't be used for glasses. In fact, an alternative name for it is Lensa-Lensa-Lensa-Lensoid. Well, I think you already know why. If not, it's because there are at least four lenses and a cardioid. A cardioid is a degenerate case of a limaçon (a polar curve of the form r = a + b cos θ). A lens is the intersection of two disks. One of the curves is almost a cardioid while many of the others approximate the outer parts of limaçons with lenses replacing their inner loops. And there are other interesting shapes and more possible names...