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JOURNALS // Matematicheskii Sbornik // Archive

Mat. Sb., 2018 Volume 209, Number 10, Pages 126–140 (Mi sm8979)

An elementary proof of Poncelet's theorem on bicentric polygons

A. M. Shelekhov

Moscow State Pedagogical University

Abstract: We give a new proof of Poncelet's theorem on bicentric polygons, using a generalisation of the notion of an orthocentre for an $n$-gon. We indicate some properties of bicentric polygons and find generalisations of Euler's formula connecting the radii of the inscribed and circumscribed circles and the distance between their centres for convex $n$-gons with $n=4, 5, 6$, and also for a non-convex pentagon. In conclusion, we consider a construction of three related bicentric pentagons.
Bibliography: 6 titles.

Keywords: Poncelet's theorem on bicentric polygons, orthocentre, Euler line.

UDC: 514.112.4+514.112.6

MSC: Primary 51M04; Secondary 51N20

Received: 14.06.2017 and 19.07.2017

DOI: 10.4213/sm8979


 English version:
Sbornik: Mathematics, 2018, 209:10, 1533–1546

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© Steklov Math. Inst. of RAS, 2026