An angle bisector is defined as a line, line segment, or ray that is drawn through the vertex of an angle and divides the angle into two congruent (equivalent or equal) angles.
Here's a step-by-step guide based on the description:
1. Identify the angle that you want to bisect.
2. Draw a line, segment, or ray that starts at the vertex (the point where the two lines of the angle meet) of the angle.
3. Make sure this new line divides the angle into two smaller angles.
4. The two smaller angles created should be equal to each other. This means they are congruent. You have now bisected the angle.
The statement mentions inscribing within a circle using a compass and straightedge, which are traditional tools in geometry for constructing angles, circles and other figures. Although this activity is not necessarily involved in the creation of an angle bisector, it illustrates that this geometric concept can be put into practical use.
Therefore, considering all these points, the first definition best describes an angle bisector.