tauto
α : Type
inst✝ : DecidableEq α
a : α
r s : RegExp α
w : List α
r_ih : w ∈ RegExp.languageOf α (RegExp.derivative a r) ↔ a :: w ∈ RegExp.languageOf α r
s_ih : w ∈ RegExp.languageOf α (RegExp.derivative a s) ↔ a :: w ∈ RegExp.languageOf α s
⊢ w ∈ RegExp.languageOf α (RegExp.derivative a r) ∨ w ∈ RegExp.languageOf α (RegExp.derivative a s) ↔
    a :: w ∈ RegExp.languageOf α r ∨ a :: w ∈ RegExp.languageOf α s
no goals