| ⊦ (¬ even(i) ∨ ¬ even(j)) ∧ (even(i) ∨ even(j)) ↔ ¬ even(i) ∧ even(j) ∨ even(i) ∧ ¬ even(j) |
¬ even(i) ∨ ¬ even(j), even(i) ∨ even(j) ⊦ ¬ even(i) ∧ even(j), even(i) ∧ ¬ even(j)
¬ even(i) ∧ even(j) ∨ even(i) ∧ ¬ even(j) ⊦ (¬ even(i) ∨ ¬ even(j)) ∧ (even(i) ∨ even(j))