lean_workbook_plus_1741

Proved

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

$a^2 + b^2 + c^2 - ab - bc - ca = \sum_{\text{cyc}} \frac{(a-b)^2}{2} \ge 0$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_1741 (a b c : ℝ) : a^2 + b^2 + c^2 - a * b - b * c - c * a ≥ 0   :=  by sorry

Source