# Bisect an Angle

- Author:
- mark vasicek

- Topic:
- Constructions

## Bisect an Angle - Instructions

We start with angle A. Point B is on one of the sides.
Use the <compass tool> to construct a circle with radius AB and center at A.
Use the <intersection tool> to mark the intersection of the circle with the other side of the angle, point C.
What can you say about segments AB and AC?
Use the <compass tool> to construct two more circles, with radius AB, and centers and B and C.
These will intersect at A and at a new point.
Use the <intersection tool> to mark the second intersection, point D.
Use the <polygon tool> to construct quadrilateral ABCD. (Notice how the ORDER is important!)
How would you classify quadrilateral ABDC?
Explain why this is so.
Use the <ray tool> to construct ray AD.
How does ray AD relate to angle BAC?
(Again, order is important. The middle letter is the vertex of an angle when naming it with 3 letters).
Use the <segment tool> to construct segment BC.
How does ray AD relate to segment BC?
What special name do you have for ray AD?
Which one is doing the cutting in half (bisector), and which is being cut (bisectED).
Finally, how are angles BAD and CAD related? Explain why.