Proof by Contrapositive

• Read carefully pages 84 through 89 (section 3.3)
• Some key questions to answer:
  1. What does the contrapositive theorem (theorem 3.9) state?
  2. Describe in detail how a proof by contrapositive would go.
  3. Show examples of proofs by contrapositive.
  4. When do you think would we want to employ a proof by contrapositive?
  5. How do we prove results that are stated as a biconditional?
  6. Study carefully all example proofs in this section.
• Practice problems from section 3.3 (page 94): 3.17, 3.19, 3.21, 3.25