MAT 3100 Introduction to Proof 04 Methods of Proof II http: //myhome. spu. edu/lauw
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Preview of More Reviews l Indirect Proofs • Contradiction • Proof by Contrapositive is considered as a • • special case of proof by contradiction Proof by cases Existence proofs
Proof by Contradiction l Proof by Contrapositive l Proof by Contradiction
Example 1 Analysis Proof
Proof by Contradiction Analysis Proof by Contradiction of If-then Theorem • Suppose the negation of the conclusion is true. • Find a contradiction. • State the conclusion.
Proof by Contradiction l The method also work with statements other then If P then Q
Example 2 Analysis Proof
Pause Here l Classwork
Proof by Cases
Example 3 Analysis Proof
Proof by Cases Analysis Proof by Cases of If-then Theorem • Split the domain of interest into cases. • Prove each case separately. • State the conclusion. • Note that the cases do not have to be mutually exclusive. They just have to cover all elements in the domain.
Existence Proofs
Example 4 Analysis Proof
Existence Proofs Analysis Existence Proof • Prove the statement by exhibiting an element in the domain of interest that satisfies the given conditions. • State the conclusion.
Group Explorations 04 l l Very fun to do. Keep your voices down…you do not want to spoil the fun for the other groups.