subst_eqs
case intro
x : ℕ
F : List Formula
δ : List Program
a : ℕ
x_notin : ¬x = a
left✝ : F = []
right✝ : δ = [·a]
⊢ (∀ x_1 ∈ F, x ∉ vocabOfFormula x_1) ∧ ∀ x_1 ∈ δ, x ∉ vocabOfProgram x_1
case intro.refl.refl
x a : ℕ
x_notin : ¬x = a
⊢ (∀ x_1 ∈ [], x ∉ vocabOfFormula x_1) ∧ ∀ x_1 ∈ [·a], x ∉ vocabOfProgram x_1