lean_workbook_plus_40366

Proved

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

What is the correct AM-GM solution to the inequality $(a^2+b^2)(c^2+d^2) \geq (ac+bd)^2$ ?

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_40366 (a b c d : ℝ) : (a^2 + b^2) * (c^2 + d^2) ≥ (a * c + b * d)^2   :=  by sorry

Source