1. 1.3 BISECTING AN ANGLE An angle is the union of two non-collinear rays with the same end point. (Two special cases outside this definition are zero and straight angles. We will define them tomorrow.) Interior of an angle – the smaller of the two regions that are formed. Exterior of an angle - the larger of the two areas that are formed. Measure of an angle – the smallest amount of rotation about the vertex from one ray to the other, measured in degrees or radians (degrees for now). NAMING: ∠ XYZ, or ∠ ZYX or ∠ Y

2. Another way to say it is an angle bisector is a line or ray that divides an angle into two congruent angles. Congruent – basically means that I could put one figure on top of the other having them match perfectly.

3. Constructing an Angle Bisector Circle A and Circle B are congruent. WE will prove why this construction works a little later in the course. It is based on congruent triangles. FOR NOW: Please construct this in your notebook using a compass and straight edge. Think for a moment before you begin about the order in which you will do this.