exact c1
case neg.a.a
D : Type
I : Interpretation D
E : Env
σ : VarName → VarName
binders : Finset VarName
F F' : Formula
σ' : VarName → VarName
binders' : Finset VarName
x y : VarName
ih_1 : ∀ (v : VarName), v = x ∨ v = y → v ∉ binders' → σ' v ∉ binders'
V V' : VarAssignment D
h2 : ∀ v ∈ binders', V v = V' (σ' v)
h3 : ∀ (v : VarName), σ' v ∉ binders' → V v = V' (σ' v)
h4 : ∀ v ∈ binders', v = σ' v
c1 : x ∉ binders'
⊢ x ∉ binders'
no goals