rcases partInt with ⟨θ, pI_prop⟩
φ ψ : Formula
hyp : φ⊨ψ
X : TNode := ([φ], [~ψ], none)
ctX : ClosedTableau ([], []) X
partInt : PartInterpolant X
⊢ ∃ θ, Interpolant φ ψ θ
case mk
φ ψ : Formula
hyp : φ⊨ψ
X : TNode := ([φ], [~ψ], none)
ctX : ClosedTableau ([], []) X
θ : Formula
pI_prop : isPartInterpolant X θ
⊢ ∃ θ, Interpolant φ ψ θ