When a geometric object is rotated, it is rotated about a given point through a given angle. To use GeoMaster on the TI-84 Plus graphing calculator to rotate an already constructed geometric object, follow these steps:

1. Construct the point of rotation.

The point about which rotation occurs can be one of the points on the already constructed object. The first image shows that the already constructed triangle is to be rotated about the point.

2. Press [GRAPH][TRACE][3] to select the Rotation tool from the TRFM menu.

3. Use the arrow keys to move the cursor to the object you want to rotate and press [ENTER].

GeoMaster can rotate only one object at a time. The object to be rotated appears as a dashed figure.

4. Use the arrow keys to move the cursor to the point of rotation and press [ENTER].

5. Use the keypad to enter the degree measure of the angle of rotation.

As you begin to enter the angle,

appears in the lower-left corner of the screen, and the calculator places your angle measure after this symbol. You can enter your angle as a negative number to rotate in the clockwise direction or as a positive number to rotate in the counterclockwise direction. The second image illustrates that the triangle is about to be rotated 30 degrees in the clockwise direction.

Instead of entering the measure of the angle of rotation, you can repeatedly press [+] and/or [–] to rotate the object about the point. Each time you press [+], the object is rotated 5 degrees in the counterclockwise direction; [–] rotates it 5 degrees clockwise.

6. Press [ENTER].

The original placement of the object vanishes, and the rotation of the object appears on the screen.

The Rotation tool remains active until you deactivate it. So if you want to rotate another object, repeat Steps 3 through 6. When you are finished using the tool, deactivate it by pressing [CLEAR] or by selecting another menu item.