lean_workbook_plus_22774

Proved

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

Prove that if $a, b \in \mathbb{R}$ , then $ab > 0$ if both $a$ and $b$ have the same sign.

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_22774 (a b : ℝ) : (a > 0 ∧ b > 0) ∨ (a < 0 ∧ b < 0) → a * b > 0   :=  by sorry

Source