How to Measure an Angle with GeoMaster
For GeoMaster on the TI84 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 measure does not contain the small squares representing these three defining points, then GeoMaster cannot measure it. After you have constructed the three points defining your angle, GeoMaster can find its measure.
GeoMaster measures all angles in degrees — even if the Mode is set to radian measure.
To find the degree measure of an already constructed angle containing three defining points, follow these steps:

Press [GRAPH][ZOOM][3] to select the Angle tool from the MEAS menu.
The tool you selected appears in the upperright corner of the screen.

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.

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.

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 degree measure of the angle appears near the location of the cursor.

Use the arrow keys to move the angle measure to the location of your choice and press [ENTER] to anchor that location.
After measuring an angle, the Angle tool remains active until you deactivate it. So if you want to measure more angles, repeat Steps 2 through 5. When you are finished using the tool, deactivate it by pressing [CLEAR] or by selecting another menu item.