| ((n + 1) * (n + 2)) / 2 < ((m + 1) * (m + 2)) / 2 ↔ n < m, m ≤ n, m0 ≤ m ⊦ (m * (m + 1)) / 2 + m0 < ((n + 1) * (n + 2)) / 2 |
m0 ≤ m, m ≤ n ⊦ (m * (m + 1)) / 2 + m0 < ((n + 1) * (n + 2)) / 2, n < m, ((n + 1) * (n + 2)) / 2 < ((m + 1) * (m + 2)) / 2
Used simplifier rules: ⊦ m < n → (n ≤ m ↔ false); (s)