English
For nonempty ι, the coercion commutes with iSup: the coe of iSup equals iSup of coerced elements.
Русский
Для непустого ι отображение коe commuting с iSup: коe(iSup i) = iSup i (коe S(i)).
LaTeX
$$$$ \uparrow(\operatorname{iSup} S) = \operatorname{iSup}\big( \uparrow( S(i) ) \big). $$$$
Lean4
theorem coe_iSup [ConditionallyCompleteLattice α] {a b : α} (h : a ≤ b) [Nonempty ι] {S : ι → Set.Icc a b} :
have : Fact (a ≤ b) := ⟨h⟩
↑(iSup S) = (⨆ i, S i : α) :=
(Set.Icc.coe_sSup h (range_nonempty S)).trans (congrArg sSup (range_comp Subtype.val S).symm)