lean_workbook_plus_79945

Proved

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

Similar ineq (easier and classical) $a^2+b^2+c^2=1$ <=> $\frac{1}{4+a^2-2bc} \le \frac{9}{11}$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_79945 (a b c : ℝ) (ha : a^2 + b^2 + c^2 = 1) : 1 / (4 + a^2 - 2 * b * c) ≤ 9 / 11   :=  by sorry

Source