lean_workbook_plus_26078

Proved

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

Prove that if $f : \mathbb{R} \to \mathbb{R}$ is a continuous function such that $f(f(x)) = x$ for all $x \in \mathbb{R}$ , then $f$ is bijective.

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_26078 (f : ℝ → ℝ) (hf : Continuous f) (h : ∀ x, f (f x) = x) : Function.Bijective f   :=  by sorry

Source