simp only [isFreeIn]
case h1.a.a.a.h2
P Q : Formula
v : VarName
h1 : ¬isFreeIn v Q
⊢ ¬isFreeIn v (forall_ v (P.imp_ Q))
case h1.a.a.a.h2
P Q : Formula
v : VarName
h1 : ¬isFreeIn v Q
⊢ ¬(¬True ∧ (isFreeIn v P ∨ isFreeIn v Q))