Introduction to Geometry: Rays and Angles

Bisector of an Angle

The bisector of an angle is a segment or a ray that passes through the vertex of the angle and divides it into two congruent angles.

In the figure below, AP is the bisector of QPM, since the measure of angle Q P A equals the measure of angle A P M equals 55 degrees. This means that AP divides angle QPM into two congruent angles. Ray PA is the angle bisector of angle QPM.

angle Q P M with bisector P A drawn so that it makes two angles equals to 55 degrees each