apply IsDeduct.mp_ Q
case h1.h1.h1
P Q : Formula
v : VarName
⊢ IsDeduct {forall_ v Q, forall_ v ((P.imp_ Q).and_ (Q.imp_ P))} P
case h1.h1.h1.a
P Q : Formula
v : VarName
⊢ IsDeduct {forall_ v Q, forall_ v ((P.imp_ Q).and_ (Q.imp_ P))} (Q.imp_ P)

case h1.h1.h1.a
P Q : Formula
v : VarName
⊢ IsDeduct {forall_ v Q, forall_ v ((P.imp_ Q).and_ (Q.imp_ P))} Q