1.3. Congruent Angles and Angle Bisectors http://www.ck12.org
Here,
−→
BAand−→
BCmeet to form an angle. An angle is labeled with an “^6 ” symbol in front of the three letters used to
label it. This angle can be labeled^6 ABCor^6 CBA.Always put the vertex (the common endpoint of the two rays)
in the middle of the three points.It doesn’t matter which side point is written first.
Anangle bisectoris a ray that divides an angle into two congruent angles, each having a measure exactly half of the
original angle. Every angle has exactly one angle bisector.
BDis the angle bisector of^6 ABC
(^6) ABD∼= (^6) DBC
m^6 ABD=
1
2
m^6 ABCLabel equal angles withangle markings, as shown below.
Investigation:Constructing an Angle Bisector
- Draw an angle on your paper. Make sure one side is horizontal.
- Place the pointer on the vertex. Draw an arc that intersects both sides.