aesop
case inr
X : Finset Formula
ψ ϕ : Formula
psi_in_X : ψ ∈ X
sub_voc : vocabOfFormula ϕ ⊆ vocabOfFormula ψ
a : Char
h✝ : ∃ a_1, (¬a_1 = ψ ∧ a_1 ∈ X) ∧ a ∈ vocabOfFormula a_1
⊢ ∃ a_1 ∈ X, a ∈ vocabOfFormula a_1
no goals