A direct proof of a theorem of Blaschke and Lebesgue

  • Evans M. HarrellEmail author


The Blaschke-Lebesgue Theorem states that among all planar convex domains of given constant width B the Reuleaux triangle has minimal area. It is the purpose of this article to give a direct proof of this theorem by analyzing the underlying variational problem. The advantages of the proof are that it shows uniqueness (modulo rigid deformations such as rotation and translation) and leads analytically to the shape of the area-minimizing domain. Most previous proofs have relied on foreknowledge of the minimizing domain. Key parts of the analysis extend to the higher-dimensional situation, where the convex body of given constant width and minimal volume is unknown.

Math Subject Classifications

52A10 52A15 52A38 49O10 

Key Words and Phrases

convex body constant width Reuleaux 


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Copyright information

© Mathematica Josephina, Inc. 2002

Authors and Affiliations

  1. 1.School of MathematicsGeorgia TechAtlanta

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