# σ = ⌜n⌝ ⊦ # σ = ∞, σ + σ⊥ = σ⊥ ↔ σ = σ⊥ to n
Used simplifier rules: ⊦ n∞ ≠ ∞ → (n = n∞.n ↔ n∞ = ⌜n⌝ ); (elim) Used terms: # σ, m