lean_workbook_plus_57779

Proved

by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

Let $a,b,c$ be the sides of a triangle .Then prove that \n $\frac{a-b}{b+c} + \frac{b-c}{c+a} + \frac{c-a}{a+b} <0.5$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_57779 (a b c : ℝ) (hx: a > 0 ∧ b > 0 ∧ c > 0) (hab : a + b > c) (hbc : b + c > a) (hca : a + c > b) : (a - b) / (b + c) + (b - c) / (c + a) + (c - a) / (a + b) < 1 / 2   :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook

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