cases h1_right_right_right_right
P_u P_v : Formula
u v : VarName
h1_left : ¬isFreeIn v P_u
h1_right_left : ¬isFreeIn u P_v
h1_right_right_left : fastAdmits u v P_u
h1_right_right_right_left : fastAdmits v u P_v
h1_right_right_right_right : P_v = fastReplaceFree u v P_u ∧ P_u = fastReplaceFree v u P_v
⊢ IsProof ((forall_ u P_u).iff_ (forall_ v P_v))
case intro
P_u P_v : Formula
u v : VarName
h1_left : ¬isFreeIn v P_u
h1_right_left : ¬isFreeIn u P_v
h1_right_right_left : fastAdmits u v P_u
h1_right_right_right_left : fastAdmits v u P_v
left✝ : P_v = fastReplaceFree u v P_u
right✝ : P_u = fastReplaceFree v u P_v
⊢ IsProof ((forall_ u P_u).iff_ (forall_ v P_v))