Coin Paradox

CoinParadoxCoin rollowing around an equal coin

After a half rotation of the coin on the left around the central coin (of the same radius), the coin undergoes a complete rotation. In other words, a coin makes two complete rotations when rolled around the boundary of an identical coin. This fact is readily apparent in the generation of the cardioid as one disk rolling on another.

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Pappas, T. "The Coin Paradox." The Joy of Mathematics. San Carlos, CA: Wide World Publ./Tetra, p. 220, 1989.Steinhaus, H. Mathematical Snapshots, 3rd ed. New York: Dover, p. 145, 1999.

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Coin Paradox

Cite this as:

Weisstein, Eric W. "Coin Paradox." From MathWorld--A Wolfram Web Resource.

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