Arbitrary Curves of Constant Width

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Both the circle and the Reuleaux triangle are examples of curves of constant width. Such curves, if fitted into a square, can rotate in constant contact with all four sides. Any triangle can serve as a template for a curve of constant width by putting three pairs of arcs of circles around it, centered at each of the three vertices, as shown by this Demonstration.
Barbier's theorem[1] proves that a curve with constant width 1 has a perimeter of π.

References

[1] Wikipedia, Barbier's theorem.

External Links

A Rolling Reuleaux Triangle
A Rotating Reuleaux Triangle
Curve of Constant Width (Wolfram MathWorld)
Curves and Surfaces of Constant Width
Reuleaux Triangle (Wolfram MathWorld)

Permanent Citation

Ed Pegg Jr
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​"Arbitrary Curves of Constant Width"​
​http://demonstrations.wolfram.com/ArbitraryCurvesOfConstantWidth/​
​Wolfram Demonstrations Project​
​Published: January 15, 2013