1. CONGRUENT ANGLES & BISECTOR OF AN ANGLE

2. Definition of Congruent Angles Two angles are said to be congruent if and only if they have the same measure. There is a phrase if & only ifwhich means that the definition is two way. 1) If the angles are congruent, then they are equal. 2) If the angles are equal, then they are congruent.

3. ILLUSTRATION: In the figure, If A = 55 ° and B = 55 °, then A B If A B, then m A =m B A 55° 55° B

4. Definition of Bisector of an Angle The bisector of an angle is a ray that divides an angle into two congruent angles. ILLUSTRATION: In the figure, if ray BF A F Is an angle bisector, then It divides ABC into two B C equal parts. And ABF CBF. NOTE: LIKE MARKINGS INDICATES EQUAL PARTS

5. Angle Addition Postulate If F is in the interior of ABC, then m ABF +m FBC= m ABC. Then ray BF is called angle bisector of the angle. A F B C NOTE: LIKE MARKINGS INDICATES EQUAL PARTS