Rationality of certain triangle tilings

Fuente: arXiv
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Hauptverfasser: Beeson, Michael, Zhang, Yan X
Format: Preprint
Veröffentlicht: 2026
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author Beeson, Michael
Zhang, Yan X
author_facet Beeson, Michael
Zhang, Yan X
contents We consider tilings of a triangle $ABC$ by congruent copies of a triangle that has one angle equal to $120^\circ$, has non-commensurable angles (that is, not all angles are rational multiples of $π$), and is not similar to $ABC$. We prove that any such tiling has commensurable sides, meaning that the side lengths can be taken to be integers after scaling. As a consequence, we show that outside of a couple of special cases, a triangle (allowing all angles) tiling must either have commensurable angles or commensurable sides (that is, all sides have rational ratios).
format Preprint
id arxiv_https___arxiv_org_abs_2604_01314
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Rationality of certain triangle tilings
Beeson, Michael
Zhang, Yan X
Combinatorics
51M20, 51M04, 05E40
We consider tilings of a triangle $ABC$ by congruent copies of a triangle that has one angle equal to $120^\circ$, has non-commensurable angles (that is, not all angles are rational multiples of $π$), and is not similar to $ABC$. We prove that any such tiling has commensurable sides, meaning that the side lengths can be taken to be integers after scaling. As a consequence, we show that outside of a couple of special cases, a triangle (allowing all angles) tiling must either have commensurable angles or commensurable sides (that is, all sides have rational ratios).
title Rationality of certain triangle tilings
topic Combinatorics
51M20, 51M04, 05E40
url https://arxiv.org/abs/2604.01314