lean_workbook_plus_9021

Proved

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

Cauchy-Schwarz inequality: $(a^2+b^2+c^2)(x^2+y^2+z^2)\geq (ax+by+cz)^2$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_9021 (a b c x y z : ℝ) :
  (a^2 + b^2 + c^2) * (x^2 + y^2 + z^2) ≥ (a * x + b * y + c * z)^2   :=  by sorry

Source