English
If |a1 - b1| < ε and |a2 - b2| < ε, then |max(a1,a2) - max(b1,b2)| < ε.
Русский
Если |a1 - b1| < ε и |a2 - b2| < ε, то |max(a1,a2) - max(b1,b2)| < ε.
LaTeX
$$$\forall \varepsilon>0,\ a_1,a_2,b_1,b_2\in \alpha,\ |a_1-b_1|<\varepsilon \land |a_2-b_2|<\varepsilon \Rightarrow |\max(a_1,a_2)-\max(b_1,b_2)|<\varepsilon.$$$
Lean4
theorem rat_sup_continuous_lemma {ε : α} {a₁ a₂ b₁ b₂ : α} :
abs (a₁ - b₁) < ε → abs (a₂ - b₂) < ε → abs (a₁ ⊔ a₂ - b₁ ⊔ b₂) < ε := fun h₁ h₂ =>
(abs_max_sub_max_le_max _ _ _ _).trans_lt
(max_lt h₁ h₂)
-- so named to match `rat_add_continuous_lemma`