1. Section 2.2 Inductive and Deductive Reasoning

2. Definition: Conjecture an unproven statement that is based on observations or given information.

3. Definition: Counterexample a specific case for which a conjecture is false.

4. Counterexample Find a counter example to show that the following conjecture is false. The sum of two numbers is always greater than the larger number.

5. This applies when one statement is conditional and a second statement confirms the hypothesis of the conditional. The conclusion is then confirmed. Here is an example. The Law of Detachment

6. If it is Friday, then Mary goes to the movies. It is Friday. What conjecture can you make from the above statements? Deductive Reasoning

7. If two angles form a linear pair, then they are supplementary. Angle 1 and Angle 2 are a linear pair. Deductive Reasoning

8. If two angles form a linear pair, then they are supplementary. Angle 1 and Angle 2 are supplementary. Deductive Reasoning

9. This applies when you have two conditional statements. The conclusion of one, confirms the hypothesis of the other. In this case our result is still a conditional with the first hypothesis and the second conclusion. (I call this the “Oreo Cookie” Law.) Here is how it works… The Law of Syllogism

10. If it is Friday, then Mary goes to the movies. If Mary goes to the movies then she gets popcorn. Combine the two above conditional statements into one conditional statement. Deductive Reasoning

11. If two angles form a linear pair, then they are supplementary. If two angles are supplementary then their sum is 180 degrees. Deductive Reasoning

12. If a polygon is regular, then all angles in the interior of the polygon are congruent. If a polygon is regular, then all of its sides are congruent. Why can’t these two statements be combined like the last example. Deductive Reasoning

13. Practice A5 P.80:17-24