PreprintCC BY 4.0arXiv
A Proof of Liu's Conjecture on the Fundamental Triangle Inequality
Abstract
Let a,b,c be the side lengths of a triangle, and let R and r denote its circumradius and inradius, respectively. Liu proposed the conjecture ∑cyc ((a(b+c−a))/bc)k ≥ 2+(2r/R)k, k>1, with the reverse inequality for k<1. We prove this conjecture by reducing it to an algebraic inequality for three positive variables with prescribed sum and product. We also determine the equality cases.
Related
- A proof of Alexander’s Conjecture on an Inequality of Cassels
- A Sharp Fisher-Information Inequality for Boolean Pairs: Proof of the Amari--Kobayashi Conjecture
- A proof of Chvátal's conjecture via a sharp correlation inequality
- Proof of Nobori's generalized Böttcher-Wenzel inequality conjecture
- A proof of the strong Gaussian product inequality conjecture
BibTeX
@misc{batbold2026proof,
title = {{A Proof of Liu's Conjecture on the Fundamental Triangle Inequality}},
author = {Tserendorj Batbold},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10633},
eprint = {2609.10633},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10633},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Proof of Liu's Conjecture on the Fundamental Triangle Inequality
AU - Tserendorj Batbold
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.10633
UR - https://arxiv.org/abs/2609.10633
AB - Let a,b,c be the side lengths of a triangle, and let R and r denote its circumradius and inradius, respectively. Liu proposed the conjecture ∑_cyc ((a(b+c−a))/bc)^k ≥ 2+(2r/R)^k, k>1, with the reverse inequality for k<1. We prove this conjecture by reducing it to an algebraic inequality for three positive variables with prescribed sum and product. We also determine the equality cases.
ER -