1. Undefined Terms and Definitions 2-2A Why do we need undefined terms? What is a plane? What is a biconditional statement?

2. Undefined terms Name two undefined terms that we simply “understand”. Point Line

3. Third Undefined Term Plane: a flat surface that extends infinitely. It has infinite length and width, but has not thickness. A plane is named by a single capital letter. P

4. Definition Coplanar points: points that lie in the same plane. A B C D P

5. Noncoplanar points Points that do not lie on the same plane. A B C D P Q

6. Critical Attributes Turn to page 109 in your book.

7. What Makes a Midpoint? Turn to the Explore on page 110.

8. Definition of Biconditional Statement When both a conditional and its converse are true, they are combined into one statement using the connector phrase “if and only if”. “ if and only if”

9. Definition Point M is the midpoint of AB if and only if it divided AB into two congruent segments, AM and MB. ABM

10. Both of the following statements are true. If M is the midpoint of AB, then it divides AB into two congruent segments. If a point M divided AB into two congruent segments, then it is the midpoint of AB. AB M

11. Assignment 2-2A Page 111, 1-6, 9-12, 19, 20