English
Using a dual construction, galois connections for swapped and dual components yield sInf(image2 u s t) = sSup s? or related. Here we state a dual equality form.
Русский
С использованием двойственной конструкции связи Галуа для swapped и dual-компонент получаем равенство sInf(image2 u s t) = sSup s (или близкое по двойственной формулировке).
LaTeX
$$$$ sInf(image2\\ u\\ s\\ t) = sSup(s)???? $$$$
Lean4
theorem l_sup_u [SemilatticeSup α] [SemilatticeSup β] (gi : GaloisInsertion l u) (a b : β) : l (u a ⊔ u b) = a ⊔ b :=
calc
l (u a ⊔ u b) = l (u a) ⊔ l (u b) := gi.gc.l_sup
_ = a ⊔ b := by simp only [gi.l_u_eq]