Using a truth table, determine which formula is a tautology.
(P⇒Q)⇔(¬Q⇒¬P)(P \Rightarrow Q) \Leftrightarrow (\neg Q \Rightarrow \neg P)(P⇒Q)⇔(¬Q⇒¬P)
P⇒(P∧Q)P \Rightarrow (P \wedge Q)P⇒(P∧Q)
(P∨Q)⇒P(P \vee Q) \Rightarrow P(P∨Q)⇒P
P∧¬PP \wedge \neg PP∧¬P