# Edit Create an Image Page: Cardioid

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Image Title*: A Cardioid is a pattern defined by the path of a point of the circumference of a circle that rotates around another circle. [[Image:cardioid 1.gif|left|thumb|150px]] [[Image:Apple_cardioid3.jpg|right|150px]] A cardioid is defined by the path of a point on the circumference of a circle of radius R that is rolling without slipping on another circle of radius R. Its name is derived from Greek work ''kardioedides'' for heart-shaped, where ''kardia'' means heart and ''eidos'' means shape, though it is actually shaped more like the outline of the cross section of an apple. The cardioid was first studied by Ole Christensen Roemer in 1674 in an effort to try to find the best design for gear teeth. However, the curve was not given its name until an Italian mathematician, Johann Castillon, used it in a paper in 1741. Since the cardioid is also a [[Roulette|roulette]], more specifically an epicycloid, and a special case of a {{EasyBalloon|Link=Limacon|Balloon=A limacon is a circle rolled around another circle of equal radius. It may have inner and outer loops, be heart-shaped, or be oval, depending on the position of the point tracing the curve.}} of Pascal, it is believed that it could have originated from Etiene Pascal's studies.