1. 5-5 Indirect Proof

2. Indirect Reasoning: all possibilities are considered and then all but one are proved false. The remaining possibility must be true

3. Indirect Proof: a proof involving indirect reasoning WRITING AN INDIRECT PROOF: In the first step of an indirect proof you assume as true opposite of what you want to prove.

4. Problem 1: Writing the First Step of an Indirect Proof Suppose you want to write an indirect proof of each statement. As the first step of the proof, what would you assume? An integer n is divisible by 5.

5. Suppose you want to write an indirect proof of each statement. As the first step of the proof, what would you assume? You do not have soccer practice today.

6. Problem 2: Identifying Contradictions Which two statements contradict each other?

8. Problem 3: Writing an Indirect Proof