case cons xs_hd xs_tl xs_ih =>
  simp
  simp only [isBoundIn]
  simp only [xs_ih]
  tauto
P : Formula
x xs_hd : VarName
xs_tl : List VarName
xs_ih : isBoundIn x (List.foldr forall_ P xs_tl) ↔ x ∈ xs_tl ∨ isBoundIn x P
⊢ isBoundIn x (List.foldr forall_ P (xs_hd :: xs_tl)) ↔ x ∈ xs_hd :: xs_tl ∨ isBoundIn x P
no goals