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Beginning Activity Beginning Activity 2: Converse and Contrapositive

We now define two important conditional statements that are associated with a given conditional statement.

Definition.

If \(P\) and \(Q\) are statements, then

  • The converse of the conditional statement \(P \to Q\) is the conditional statement \(Q \to P\text{.}\)

  • The contrapositive of the conditional statement \(P \to Q\) is the conditional statement \(\mynot Q \to \mynot P\text{.}\)

1.

For the following, the variable \(x\) represents a real number. Label each of the following statements as true or false.

(a)

If \(x = 3\text{,}\) then \(x^2 = 9\text{.}\)

(b)

If \(x^2 = 9\text{,}\) then \(x = 3\text{.}\)

(c)

If \(x^2 \ne 9\text{,}\) then \(x \ne 3\text{.}\)

(d)

If \(x \ne 3\text{,}\) then \(x^2 \ne 9\text{.}\)

3.

Complete appropriate truth tables to show that

(a)

\(P \to Q\) is logically equivalent to its contrapositive \(\mynot Q \to \mynot P\text{.}\)

(b)

\(P \to Q\) is not logically equivalent to its converse \(Q \to P\text{.}\)