TABLE OF LOGICAL EQUIVALENCES notation: == logical equivalence; -> implication; ^ AND; v OR; ~ NOT; <-> biconditional; XOR exclusive or; Precedence high to low: () ~ ^ v -> <-> ============================================================================= IDENTITY LAWS p ^ T == p p v F == p DOMINATION LAWS p v T = T p ^ F = F NEGATION LAWS p v ~p == T p ^ ~p == F IDEMPOTENT LAWS p v p == p p ^ p == p COMMUTATIVITY (p ^ q) == (q ^ p) (p v q) == (q v p) ASSOCIATIVITY (p ^ q) ^ r == p ^ (q ^ r) (p v q) v r == p v (q v r) DOUBLE NEGATION ELIMINATION ~(~p) == p CONTRAPOSITION p -> q == ~q -> ~p IMPLICATION ELIMINATION p -> q == ~p v q BICONDITIONAL ELIMINATION p <-> q == (p -> q)^(q -> p) == (~p v q)^(~q v p) == (~p ^ ~q) v (q ^ p) DE MORGAN'S ~( p ^ q) == ~p v ~q ~( p v q) == ~p ^ ~ q DISTRIBUTIVITY OF ^ OVER v AND v OVER ^ p ^ (q v r) == (p ^ q) v ( p ^ r) p v (q ^ r) == (p v q) ^ (p v r) ABSORPTION p v (p ^ q) == p p ^ (p v q) == p EQUIVALENCES FOR QUANTIFIERS Ax (P(x) ^ Q(x)) == Ax P(x) ^ Ax Q(x) Ax (P(x) v Q(x)) !== Ax P(x) v Ax Q(x) Ex (P(x) v Q(x)) == Ex P(x) v Ex Q(x) Ex (P(x) ^ Q(x)) !== Ex P(x) ^ Ex Q(x) AxAy P(x,y) == AyAx P(x,y) ~(AxAy P(x,y)) == ExEy ~P(x,y) ExEy P(x,y) == EyEx P(x,y) ~(ExEy P(x,y)) == AxAy ~P(x,y) AxEy P(x,y) !== EyAx P(x,y) ~(AxEy P(x,y)) == ExAy ~P(x,y) ExAy P(x,y) !== AyEx P(x,y) ~(ExAy P(x,y)) == AxEy ~P(x,y)