Discrete Mathematics with Applications 4th Edition

Published by Cengage Learning
ISBN 10: 0-49539-132-8
ISBN 13: 978-0-49539-132-6

Chapter 6 - Set Theory - Exercise Set 6.4 - Page 382: 17

Answer

No, it is not a statement. It is self-referential and leads to a paradox.

Work Step by Step

### Problem 17: **"This sentence is false or 1 + 1 = 3."** --- ### βœ… Determine if it's a **statement**: A **statement** must be a sentence that is **either true or false**, but not both or undefined. --- ### πŸ” Analysis: This is a **self-referential** sentence. Let’s call the entire sentence **S**: > **S**: "S is false or 1 + 1 = 3" Let’s analyze the truth value: - The second part, \(1 + 1 = 3\), is **false**. - So the sentence reduces to: \[ \text{"This sentence is false"} \lor \text{false} \Rightarrow S \equiv \text{"S is false"} \] So we have: \[ S \equiv \text{"S is false"} \] This is a **liar paradox** β€” it creates a contradiction: - If \(S\) is **true**, then it says it is **false** β‡’ contradiction. - If \(S\) is **false**, then it claims it is **false** β‡’ it is **true** β‡’ contradiction. --- ### ❌ Conclusion: Because of this contradiction, the sentence does **not** have a well-defined truth value.
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