exact IsProofAlt.mp_ h1_phi h1_psi h1_ih_1 h1_ih_2
F h1_phi h1_psi : Formula
h1_1 : IsDeduct ∅ (h1_phi.imp_ h1_psi)
h1_2 : IsDeduct ∅ h1_phi
h1_ih_1 : IsProofAlt (h1_phi.imp_ h1_psi)
h1_ih_2 : IsProofAlt h1_phi
⊢ IsProofAlt h1_psi
no goals