2. Good definitions are important in geometry (and almost every area) 
Good definitions are important in geometry (and almost every area)  It’s important that everyone understands what you’re talking about.

3. A good definition should: . Use clear, easily. understood terms. 
A good definition should:  Use clear, easily understood terms.  Be precise.  Be reversible.

4. To make definitions reversible, we typically use biconditionals. 
To make definitions reversible, we typically use biconditionals.  Uses the phrase if and only if  Symbols , , or iff.  A  B means A  B and B  A

5. A ray is an angle bisector if and only if it divides an angle into two congruent angles Write this as two if/then statements.

6. This means … If a ray is an angle bisector, then it divides an angle into 2 congruent angles. If it divides an angle into 2 congruent angles, then a ray is an angle bisector.

7. You can write a biconditional if a statement and its converse are both true.  This is why definitions are typically written as biconditionals.

8. Consider this example: A candy is an M&M if and only if it melts in your mouth but not in your hands.

9. . Is this statement true. . Is it a good definition of an. M&M. 
 Is this statement true?  Is it a good definition of an M&M?  Why or why not?

10. What could be a good definition of Bishop Garrigan High School?

11. REMEMBER biconditional (if and only if) characteristics of a good definition