Abstract
In this note we will show that an injection of the hyperbolic plane is Möbius if and only if for some $0<\theta<\pi$, $f$ preserves triangles with an interior angle equal to $\theta$.
Citation
Shihai Yang. "A characterization of Möbius transformations." Proc. Japan Acad. Ser. A Math. Sci. 84 (2) 35 - 38, February 2008. https://doi.org/10.3792/pjaa.84.35
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