lean_workbook_plus_10531

Proved

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

Derive the identity $\binom{n}{i}^2 = \binom{n}{i} \binom{n}{n-i}$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_10531 (n i : ℕ) : (n.choose i) ^ 2 = n.choose i * n.choose (n - i)   :=  by sorry

Source