exact psi_ih V
case a.h.e'_2.a
D : Type
I : Interpretation D
E : Env
σ : VarName → VarName
h1 : Function.Injective σ
phi psi : Formula
phi_ih : ∀ (V : VarAssignment D), Holds D I (V ∘ σ) E phi ↔ Holds D I V E (replaceAll σ phi)
psi_ih : ∀ (V : VarAssignment D), Holds D I (V ∘ σ) E psi ↔ Holds D I V E (replaceAll σ psi)
V : VarAssignment D
⊢ Holds D I (V ∘ σ) E psi ↔ Holds D I V E (replaceAll σ psi)
no goals