English
Let (α, ≤) be a linear ordered set. Then for all a, b, c ∈ α, we have max a (max b c) = max b (max a c).
Русский
Пусть (α, ≤) упорядочено линейно. Тогда для любых a, b, c ∈ α выполняется max a (max b c) = max b (max a c).
LaTeX
$$$ \max a (\max b c) = \max b (\max a c) $$$
Lean4
theorem left_comm (a b c : α) : max a (max b c) = max b (max a c) := by rw [← max_assoc, max_comm a, max_assoc]