This slideshow helps introduce geometric proofs. It gives key elements and types of reasons then gives several different types of proofs. Toward the end of the slideshow- the two column proof's statements and reasons are scrambled and the students are responsible for unscrambling the proof. There are also some fill in the blank for students to complete.

1. Geometric Proofs 27 October 2009

2. Geometric Proofs TWO COLUMN PROOFS FIVE KEY ELEMENTS Given Diagrams Prove Statements Reasons

3. Reasons Given Information Definitions Postulates PROPERTIES Theorems

4. Given: PROVE: STATEMENTS Reasons 1. 1. Given 2. Definition of supplementary angles 2. 3. Substitution Property 3. 4. 4. Subtraction Property 5. 5. Definition of Congruent Angles

5. Given: Prove: B 1 2 3 A C

6. Statements Reasons 1. 2. 3. 4. 5. 6. 7. 8. 1. 2. 3. 4. 5. 6. 7. 8. Given Definition of Right Angle Angle Addition Postulate Substitution Property (Steps 2 and 3) Given Definition of Congruent Angles Substitution Property (Step 4 and 6) Definitions of Complementary Angles

7. Given: Prove: A X 45˚ B C

8. QUIZ What is always the first step of a proof? Name 5 key elements of a proof. Name 5 types of reasons one can use during a proof. Measures __________: Angles and Segments are ______________. What is the last statement in a proof?

9. Statements Reasons 1. 2. 3. 4. 5. 6. 7. 8. 9. 1. 2. 3. 4. 5. 6. 7. 8. 9. Given Definitions of Angle Bisector Definitions of Congruent Angles Given Substitution Property Angle Addition Postulate Substitution Property Simplify Definition of Right Angle

10. Given: Prove: C D A B E

11. Statements Reasons 1. 2. 3. 4. 5. 1. 2. 3. 4. 5. Given Given Given Definition of Midpoint ASA (Steps 1, 4, 2)

12. Given: Prove: 1 A D 2 B C

13. Statements Reasons Converse of the Consecutive Interior Angles Theorem Given Perpendicular Transversal Theorem Given Definition of Supplementary Angles

14. Given: Prove: B D 1 2 3 4 A E C

15. Statements Reasons Substitution Property 5. 6. Given 3. 2. Corresponding Angles Postulate 2. 3. Given 1. 1. Substitution Property 4. 5. Converse of Corresponding Angles Postulate 6. 4.

16. Given: Prove: Z Y X W

17. Statements Reasons 1. 2. 3. 4. 5. 1. 2. 3. 4. 5. Segment Addition Postulate Substitution Property

18. Given: Prove: L M 4 5 O N

19. Statements Reasons 1. 2. 3. 4. 5. 6. 1. 2. 3. 4. 5. 6. Definition of Right Angle Substitution Property