English
For a proposition p with decidable truth and any constant a ∈ α, the infimum over x ∈ p of a equals a if p is true, otherwise ⊤.
Русский
Для пропозиции p с разрешимой判, и любого a ∈ α, инфимум над x ∈ p равен a если p истинно, иначе ⊤.
LaTeX
$$$$\bigwedge_{x} a = \operatorname{ite}(p, a, \top).$$$$
Lean4
theorem iInf_eq_dif {p : Prop} [Decidable p] (a : p → α) : ⨅ h : p, a h = if h : p then a h else ⊤ :=
@iSup_eq_dif αᵒᵈ _ _ _ _