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Show that(pq)(¬pr)(qr) is a tautology

Short Answer

Expert verified

(pq)(¬pr)(qr)is a tautology.

Step by step solution

01

Step1:Definition of Tautology

Tautology results in true.

02

The given statement is a tautology

We write the given statement,

\(\begin{array}{l}(p \vee q) \wedge (\neg p \vee r) \to (q \vee r)\;\, = (p \vee q) \wedge (\neg (\neg p \vee r) \vee (q \vee r))\\\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\; = (p \vee q) \wedge (p \wedge \neg r) \vee (q \vee r)\\\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\; = (p \vee q) \wedge \neg (p \wedge \neg r) \wedge \neg (q \vee r)\\\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\; = (p \vee q) \wedge (\neg p \vee r) \wedge (\neg q \vee \neg r)\end{array}\)

\(\begin{array}{l}(p \vee q) \wedge (\neg p \vee r) \to (q \vee r)\,\; = (p \vee \neg p) \wedge (q \vee \neg q) \vee (\neg r \vee r)......\left( {Associativity and commutativity} \right)\\\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\; = T \wedge T \wedge T\\\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\; = T\end{array}\)

Hence,\((p \vee q) \wedge (\neg p \vee r) \to (q \vee r)\)is a tautology.

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Most popular questions from this chapter


Use De Morgan’s laws to find the negation of each of the following statements.

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[Hint: Make a table where the rows represent the men and columns represent the color of their houses, their jobs, their pets, and their favorite drinks and use logical reasoning to determine the correct entries in the table.]

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