| ⊦ (σ to n) + ((σ from n) to n1) = σ to n + n1, # σ < ⌜n⌝ + ⌜n1⌝ |
⊦ σ0 = σ1 ↔ # σ0 = # σ1 ∧ (∀ n. ⌜n⌝ < # σ0 → σ0[n] = σ1[n])
⊦ #((σ to n) + ((σ from n) to n1)) = #(σ to n + n1) ∧ (∀ n0. ⌜n0⌝ < #((σ to n) + ((σ from n) to n1)) → ((σ to n) + ((σ from n) to n1))[n0] = (σ to n + n1)[n0]), # σ < ⌜n⌝ + ⌜n1⌝
Used terms: σ to n + n1, (σ to n) + ((σ from n) to n1)