⊦ 0 ≤ i → sqrt(i) ^2 ≤ i ∧ i < sqrt(i) +1 ^2
0 ≤ i * i → sqrt(i * i) ^2 ≤ i * i ∧ i * i < sqrt(i * i) +1 ^2 ⊦ sqrt(i * i) = abs(i)
Used terms: i * i