Legile lui DeMorgan

! (a && b) ⇔ !a || !b

! (a || b) ⇔ !a && !b

Observații: !(a < b) ⇔ a >= b

!(a>b) ⇔ a <= b

!(a>=b) ⇔ a < b

!(a<=b) ⇔ a > b

!(a == b) ⇔ a != b

!(a != b) ⇔ a ==b