Tautologia i sprzeczność

Tautology and contradiction A compound statement that is always true, regardless of what truth values are assigned to its statement variables, is called a tautology or a logic law . Such a statement is logically true . A compound statement that is always false, regardless of what truth values are assigned to its statement variables, is called a contradiction . Such a statement is logically false . List of the most important tautologies (logic laws): (1) p ⇔ p , p ⇒ p (the identity law for equivalence and implication) (2) ( p ⇒ q ) ⇔ ( ∼ q ⇒∼ p ) (the contrapositive law) (3) p ∨ ( ∼ p ) (law of ”the excluded center”) (4) ∼ [ p ∧ ( ∼ p )] (law of contradiction) ... zobacz całą notatkę