lean_workbook_plus_71909

Proved

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

Let $a,b,c,d\in \mathbb{R}$ such that $ab=1$ and $ac+bd=2$ . Prove: $1-cd\ge 0$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_71909 : ∀ a b c d : ℝ, a * b = 1 ∧ a * c + b * d = 2 → 1 - c * d ≥ 0   :=  by sorry

Source