apply Set.eq_empty_iff_forall_not_mem.mpr
t u : Th
p : Pr
h₁ : formalApplicationFunction t u ≤ ↑p
Δ : Set Form := { f | ¬formalApplication (↑t) (▲{f}) ⊆ ↑↑p }
⊢ ↑u ∩ Δ = ∅
t u : Th
p : Pr
h₁ : formalApplicationFunction t u ≤ ↑p
Δ : Set Form := { f | ¬formalApplication (↑t) (▲{f}) ⊆ ↑↑p }
⊢ ∀ (x : Form), ¬x ∈ ↑u ∩ Δ