English
For any a and any set s, a is disjoint from sSup s if and only if a is disjoint from every member of s.
Русский
Для любых a и множества s: a несовместим с sSup s тогда и только тогда, когда a несовместим с каждым элементом s.
LaTeX
$$$\operatorname{Disjoint}\left(a, \operatorname{sSup} s\right) \iff \forall b \in s,\ \operatorname{Disjoint}(a,b)$$$
Lean4
theorem disjoint_sSup_iff {s : Set α} : Disjoint a (sSup s) ↔ ∀ b ∈ s, Disjoint a b := by
simpa only [disjoint_comm] using @sSup_disjoint_iff