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We describe four special families of ellipse-inscribed Poncelet triangles about the incircle which maintain certain triangle centers stationary and which also display interesting conservations.

Metric Geometry · Mathematics 2025-12-23 Ronaldo A. Garcia , Mark Helman , Dan Reznik

We study loci and properties of a Parabola-inscribed family of Poncelet polygons whose caustic is a focus-centered circle. This family is the polar image of a special case of the bicentric family with respect to its circumcircle. We…

Metric Geometry · Mathematics 2022-01-26 Filipe Bellio , Ronaldo Garcia , Dan Reznik

We tour several Euclidean properties of Poncelet triangles inscribed in an ellipse and circumscribing the incircle, including loci of triangle centers and envelopes of key objects. We also show that a number of degenerate behaviors are…

Dynamical Systems · Mathematics 2025-12-29 Mark Helman , Ronaldo A. Garcia , Dan Reznik

We show that the focus of the Kiepert in-parabola remains stationary over a family of circle-inscribed Poncelet triangles which contain an equilateral triangle.

Metric Geometry · Mathematics 2025-12-19 Mark Helman , Ronaldo A. Garcia , Dan Reznik

We study families of triangles that are inscribed in a fixed circle and circumscribed about a central conic, extending the classical Chapple--Euler relation within the framework of Poncelet geometry. We establish several geometric…

General Mathematics · Mathematics 2026-04-01 Mohammad Hassan Murad

We study quadrilaterals inscribed and circumscribed about conics. Our research is guided by experiments in software Cinderella. We extend the known results in projective geometry of conics and show how modern mathematical software brings…

Algebraic Geometry · Mathematics 2013-03-25 Djordje Baralic , Branko Grbic , Djordje Zikelic

We study triangles and quadrilaterals which are inscribed in a circle and circumscribed about a parabola. Although these are particular cases of the celebrated Poncelet's Theorem, in this paper we {\it do not assume} the theorem but prove…

History and Overview · Mathematics 2026-03-10 Vladimir Dragović , Mohammad Hassan Murad

The dynamic geometry of the family of 3-periodics in the Elliptic Billiard is mystifying. Besides conserving perimeter and the ratio of inradius-to-circumradius, it has a stationary point. Furthermore, its triangle centers sweep out…

Dynamical Systems · Mathematics 2021-08-13 Dan Reznik , Ronaldo Garcia , Jair Koiller

We present a theory which predicts if the locus of a triangle center over certain Poncelet triangle families is a conic or not. We consider families interscribed in (i) the confocal pair and (ii) an outer ellipse and an inner concentric…

Metric Geometry · Mathematics 2021-12-14 Mark Helman , Dominique Laurain , Dan Reznik , Ronaldo Garcia

Can any secrets still be shed by that much studied, uniquely integrable, Elliptic Billiard? Starting by examining the family of 3-periodic trajectories and the loci of their Triangular Centers, one obtains a beautiful and variegated gallery…

Dynamical Systems · Mathematics 2022-10-11 Dan Reznik , Ronaldo Garcia , Jair Koiller

We prove that over a Poncelet triangle family interscribed between two nested ellipses $\mathcal{E},\mathcal{E}_c$, (i) the locus of the orthocenter is not only a conic, but it is axis-aligned and homothetic to a $90^o$-rotated copy of…

Metric Geometry · Mathematics 2025-08-14 Ronaldo A. Garcia , Mark Helman , Dan Reznik

The goal of this paper is an analysis of the geometry of billiards in ellipses, based on properties of confocal central conics. The extended sides of the billiards meet at points which are located on confocal ellipses and hyperbolas. They…

Metric Geometry · Mathematics 2021-05-20 H. Stachel

A Pomeron phenomenon remains a mystery. A short review of the experimental situation in diffractive physics and an account of some spectacular manifestations of the Pomeron are given.

High Energy Physics - Phenomenology · Physics 2015-06-25 A. Rostovtsev

We compare loci types and invariants across Poncelet families interscribed in three distinct concentric Ellipse pairs: (i) ellipse-incircle, (ii) circumcircle-inellipse, and (iii) homothetic. Their metric properties are mostly identical to…

Metric Geometry · Mathematics 2021-07-14 Ronaldo Garcia , Dan Reznik

Let ${\mathbf P}^2$ denote the projective plane over a finite field ${\mathbb F}_q$. A pair of nonsingular conics $({\mathcal A}, {\mathcal B})$ in the plane is said to satisfy the Poncelet triangle condition if, considered as conics in…

Algebraic Geometry · Mathematics 2016-04-05 Jaydeep Chipalkatti

The paper gives a review of very recent results related to the Poncelet Theorem, on the occasion of its bicentennial. We are telling the story of one of the most beautiful theorems of Geometry, recalling for the general mathematical…

Exactly Solvable and Integrable Systems · Physics 2013-03-26 Vladimir Dragovic , Milena Radnovic

If there is one polygon inscribed into some smooth conic and circumscribed about another one, then there are infinitely many such polygons. This is Poncelet's theorem. The aim of this note is to collect some (mostly classical) versions of…

alg-geom · Mathematics 2025-04-09 W. Barth , Th. Bauer

Poncelet polygons inscribed in a circle and circumscribed about conics from a confocal family naturally arise in the analysis of the numerical range and Blaschke products. We examine the behaviour of such polygons when the inscribed conic…

Dynamical Systems · Mathematics 2024-03-06 Vladimir Dragović , Milena Radnović

We analyze loci of triangle centers over variants of two-well known triangle porisms: the bicentric and confocal families. Specifically, we evoke the general version of Poncelet's closure theorem whereby individual sides can be made tangent…

Metric Geometry · Mathematics 2022-01-25 Ronaldo Garcia , Boris Odehnal , Dan Reznik

The celebrated Poncelet porism is usually studied for a pair of smooth conics that are in a general position. Here we discuss Poncelet porism in the real plane - affine or projective, when that is not the case, i.e. the conics have at least…

Algebraic Geometry · Mathematics 2025-07-08 Vladimir Dragovic , Milena Radnovic
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