Geometriae Dedicata

, Volume 125, Issue 1, pp 39–46 | Cite as

Periodic billiard paths in right triangles are unstable

  • W. Patrick HooperEmail author
Original Paper


A stable periodic billiard path in a triangle is a billiard path which persists under small perturbations of the triangle. This article gives a geometric proof that no right triangles have stable periodic billiard paths.


billiard right triangles periodic billiard paths Euclidean geometry 

Mathematics Subject Classification (2000)

Primary 37D50 


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Copyright information

© Springer Science + Business Media B.V. 2007

Authors and Affiliations

  1. 1.MathematicsNorthwestern UniversityEvanstonUSA

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