Archiv der Mathematik

, Volume 98, Issue 6, pp 571–581 | Cite as

Ptolemy circles and Ptolemy segments

  • Thomas FoertschEmail author
  • Viktor Schroeder


In this paper we characterize Ptolemy circles and Ptolemy segments up to isometry. Moreover, we present an example of a metric sphere, which is Möbius equivalent but not homothetic to the standard metric sphere with its chordal metric.


Triangle Inequality Cross Ratio Convex Curve Unbounded Component Busemann Function 
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© Springer Basel AG 2012

Authors and Affiliations

  1. 1.Institut für MathematikUniversität ZürichZürichSwitzerland

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