Theorem: LO.FirstOrder.Semiformula.fvarList_sentence (Logic/FirstOrder/Basic/Syntax/Formula.lean)

State before:
L : Language
ξ : Type u_1
n n₁ n₂✝ n₂ m m₁ m₂ m₃ : ℕ
o : Type u_2
inst✝ : IsEmpty o
p : Semiformula L o n
⊢ p.fvarList = []
Tactic:
induction p using rec' <;> simp[*, fvarList, ←neg_eq]
State after:
no goals