simp [dis]
x : ℕ
ψ φ1 φ2 : Formula
l : List Formula
⊢ repl_in_F x ψ (dis (φ1 :: φ2 :: l)) = dis (List.map (repl_in_F x ψ) (φ1 :: φ2 :: l))
x : ℕ
ψ φ1 φ2 : Formula
l : List Formula
⊢ repl_in_F x ψ (dis (φ2 :: l)) = dis (repl_in_F x ψ φ2 :: List.map (repl_in_F x ψ) l)