exact h1_ih
case a
P_r P_s : Formula
r s : VarName
P_u P_v : Formula
h1_1 : IsReplOfVarInFormula r s P_u P_v
h2 : ¬isBoundIn r P_u
h3 : ¬isBoundIn s P_u
h1_ih : IsProof ((eq_ r s).imp_ (P_u.iff_ P_v))
⊢ IsDeduct ∅ ((eq_ r s).imp_ (P_u.iff_ P_v))
no goals