| fac(j - 1) * fac(i + 1 - j) ≠ 0, (fac(j - 1) * fac(i + 1 - j)) * i1 = fac(i), (fac(i - j) * fac(j)) * i0 = (fac(j - 1) * fac(i + 1 - j)) * i1, 0 < j, 0 ≤ i, 0 ≤ j, 0 < i, j ≤ i ⊦ i0 * j = i1 * (i + 1 - j) |
(fac(i - j) * fac(j)) * i0 = fac(i), fac(i) = (fac(j - 1) * fac(i + 1 - j)) * i1, 0 < j, 0 ≤ i, 0 ≤ j, 0 < i, j ≤ i ⊦ i0 * j = i1 * (i + 1 - j)
Used simplifier rules: fac-not-zero: ⊦ fac(i) * fac(j) ≠ 0;%commutativity: ⊦ i * j = j * i; from specification int-mult%associativity: ⊦ i * j * j0 = (i * j) * j0; from specification int-mult