English
In a linear order, a < b ⊔ c iff a < b or a < c.
Русский
В линейном порядке a < b ∨ c эквивалентно a < b или a < c.
LaTeX
$$$a < b \vee c \iff a < b \lor a < c$$$
Lean4
@[simp]
theorem lt_sup_iff : a < b ⊔ c ↔ a < b ∨ a < c := by
exact
⟨fun h => (le_total c b).imp (fun bc => by rwa [sup_eq_left.2 bc] at h) (fun bc => by rwa [sup_eq_right.2 bc] at h),
fun h => h.elim lt_sup_of_lt_left lt_sup_of_lt_right⟩