1. 3.3 CPCTC and Circles Objective: After studying this lesson you will be able to apply the principle of CPCTC and recognize some basic properties of circles.

2. A C T CPCTC “Corresponding Parts of Congruent Triangles are Congruent” O D G Suppose that. Can we say that ? After we have proven two triangles are congruent we will use as a reason. Corresponding parts refer to the matching angles and sides in the respective triangles.

3. Point O is the center of the circle shown below. Definition of a circle:every point of the circle is the same distance from the center. O The center is not a part of the circle, just the outside or the “rim”. Circles are named by their centers. The circle above is named circle O or

4. P A B C Points A, B, and C lie on circle P. PA is called the radius PA, PB, and PC are called radii. Formulas to remember! Theorem:all radii are congruent

5. Given: Prove: StatementReason D B C A 1. 2. 3. 4. 5. 1. 2. 3. 4. 5. P

6. Given: Prove: Statement Reason 1. 2. 3. 4. 5. 6. 7. 8. 1. 2. 3. 4. 5. 6. 7. 8. R S T K O P M

7. Summary: When is it appropriate to use CPCTC as a reason in a proof? Homework: worksheet