10. Proof Strategies-I
The chapter introduces various proof strategies, focusing on direct proofs and several methods of indirect proof including proof by contrapositive, vacuous proof, and proof by contradiction. These proof methods are essential for validating universally quantified implications in mathematics. Examples and illustrations clarify how each strategy can be applied effectively in different contexts.
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Sections
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What we have learnt
- Different proof strategies include direct proofs, proof by contrapositive, vacuous proof, and proof by contradiction.
- Direct proof starts by assuming the premise is true and logically shows the conclusion.
- Indirect proof methods are useful when direct proof is complex or impossible, each relying on logical equivalences.
Key Concepts
- -- Direct Proof
- A method that starts with assuming the premise is true to show that the conclusion must also be true.
- -- Proof by Contrapositive
- A strategy that proves an implication by demonstrating that the negation of the conclusion leads to the negation of the premise.
- -- Vacuous Proof
- A proof method stating that an implication is true if the premise is false, regardless of the truth of the conclusion.
- -- Proof by Contradiction
- A method where one assumes the negation of the conclusion and shows that this assumption leads to a contradiction.
- -- Universally Quantified Implication
- A statement of the form 'for all x, if P(x) then Q(x)'.
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