English
If f is antitone, then f(x ⊔ y) = f x ⊓ f y when half-typed; i.e., the dual property.
Русский
Если f антитонна, то f(x ⊔ y) = f x ⊓ f y в двойственном виде.
LaTeX
$$$ [SemilatticeInf β] {f : \alpha → β} (hf : Antitone f) (x y : \alpha) : f(x \sqcup y) = f x \sqcap f y$$$
Lean4
theorem map_sup [SemilatticeInf β] {f : α → β} (hf : Antitone f) (x y : α) : f (x ⊔ y) = f x ⊓ f y :=
hf.dual_right.map_sup x y