English

Triangles and groups via cevians

Metric Geometry 2013-01-17 v2

Abstract

For a given triangle TT and a real number ρ\rho we define Ceva's triangle \CTρ(T)\CT_\rho(T) to be the triangle formed by three cevians each joining a vertex of TT to the point which divides the opposite side in the ratio ρ:(1ρ)\rho:(1-\rho). We identify the smallest interval \nMT\nR\nM_T \subset \nR such that the family \CTρ(T),ρ\nMT\CT_\rho(T), \rho\in \nM_T, contains all Ceva's triangles up to similarity. We prove that the composition of operators \CTρ,ρ\nR\CT_\rho, \rho \in \nR, acting on triangles is governed by a certain group structure on \nR\nR. We use this structure to prove that two triangles have the same Brocard angle if and only if a congruent copy of one of them can be recovered by sufficiently many iterations of two operators \CTρ\CT_\rho and \CTξ\CT_\xi acting on the other triangle.

Keywords

Cite

@article{arxiv.1109.0557,
  title  = {Triangles and groups via cevians},
  author = {Árpád Bényi and Branko Ćurgus},
  journal= {arXiv preprint arXiv:1109.0557},
  year   = {2013}
}

Comments

33 pages, 17 figures

R2 v1 2026-06-21T18:59:09.038Z