exact psi_ih j
case h2
z : String
phi psi : Formula
phi_ih : ∀ (j : ℕ), phi.freeVarSet ⊆ (Formula.open j (free_ z) phi).freeVarSet
psi_ih : ∀ (j : ℕ), psi.freeVarSet ⊆ (Formula.open j (free_ z) psi).freeVarSet
j : ℕ
⊢ psi.freeVarSet ⊆ (Formula.open j (free_ z) psi).freeVarSet
no goals