1. 1.5 Angle Bisectors

2. Angle Bisector A ray that divides an angle into 2 congruent adjacent angles. BD is an angle bisector of <ABC. B A C D

3. Ex1: If FH bisects  EFG & m  EFG=80 o, what is m  EFH? G H E F

4. #2 you try: If FH bisects  EFG & m  EFG=130 o, what is m  EFH? G H E F

5. EX #3!!: Find m  CBD x+40 o 3x-20 o * If they are congruent, set them equal to each other, then solve! x+40 = 3x-20 40 = 2x-20 60 = 2x 30 = x A B C D 3x-20 o = 3(30)-20 = 70 o

6. #4 you try!!: Find m  ABD x+40 o 3x-20 o * If they are congruent, set them equal to each other, then solve! x+40 = 3x-20 40 = 2x-20 60 = 2x 30 = x A B C D 3x-20 o = 3(30)-20 = 70 o Since both angles are congruent, 70 o +70 o =140º

7. CONSTRUCTION OF AN ANGLE BISECTOR http://www.mathopenref.com/constbisec tangle.htmlhttp://www.mathopenref.com/constbisec tangle.html

8. ANGLE BISECTOR PRACTICE USING A COMPASS & RULER, CONSTRUCT THE ANGLE BISECTOR FOR EACH PROBLEM ON THE WORKSHEET BEING PASSED OUT. COMPARE ANSWERS WITH YOUR NEIGHBOR.