⊦ σ = σ2 ↔ # σ = # σ2 ∧ (∀ n. ⌜n⌝ < # σ → σ[n] = σ2[n])
#(σ + σ⊥) = # σ⊥, # σ = ⌜n⌝ , ∀ n. ⌜n⌝ < #(σ + σ⊥) → (σ + σ⊥)[n] = (σ⊥)[n] ⊦ σ = σ⊥ to n
Used terms: σ⊥, σ + σ⊥