# How to Construct Angle Bisectors with GeoMaster

For GeoMaster on the TI-84 graphing calculator to recognize the existence of an angle, that angle must contain three defining points — the vertex and a point on each side of the angle. Also, GeoMaster recognizes a point only if it appears on the screen as a small square.

If the angle you want to bisect does not contain the small squares representing the three points defining the angle, then GeoMaster cannot bisect it. After you have constructed the three points defining your angle, GeoMaster can bisect it.

To construct the bisector of an already constructed angle containing three defining points, follow these steps:

1. Select the Angle Bisector tool from the DRAW menu.

To do this, press [WINDOW] if the Menu bar is visible at the bottom of the screen or [GRAPH][WINDOW] if it is not. Press

to move the cursor to Angle Bisector, the last menu item, and press [ENTER]. The tool you selected appears in the upper-right corner of the screen.

2. Use the arrow keys to move the cursor to an existing point on one side of the angle and press [ENTER] to anchor that point.

GeoMaster uses a small square to indicate that a point exists. If you don’t see a small square on the side of the angle, the first paragraph in this section tells you what to do about the situation.

3. Use the arrow keys to move the cursor to the vertex of the angle and press [ENTER] to anchor the vertex.

The vertex must always be the second point that defines the angle.

4. Use the arrow keys to move the cursor to an existing point on the other side of the angle and press [ENTER] to anchor that point.

The angle bisector appears as a solid line, indicating that your construction is complete.

After constructing an angle bisector, the Angle Bisector tool remains active until you deactivate it. So if you want to construct more angle bisectors, just repeat Steps 2 through 4. When you are finished using the tool, you deactivate it by pressing [CLEAR] or by selecting another menu item.