## cardioidWhen a circle rolls around another circle of the same size, any point on the moving circle traces out a cardioid. The Greeks used this fact when attempting to describe the motions of the planets. The cardioid is also the envelope of all circles with centers on a fixed circle, passing through one point on the fixed circle. In polar coordinates, it has the equation r = 2a(1 - cos θ).
It can also be described as an epicycloid with one cusp. ## Related category• PLANE CURVES | ||||||

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