A circle is determined by its center and its radius. The GeoMaster DRAW menu contains a plethora of tools that enable you to do mundane things such as construct lines, segments, triangles, polygons, and circles. To construct a circle with GeoMaster on the TI-84 Plus graphing calculator, follow these steps:

1. Select the Circle tool from the DRAW menu.

To do this, press [GRAPH][WINDOW][4]. “Circle” in the upper-right corner of the first screen illustrates that the Circle tool is active.

2. Use the arrow keys to move the cursor to the location on the screen where you want to place the center of the circle. Press [ENTER] to anchor this point.

As you move the cursor, its coordinates are displayed at the bottom of the screen and the center of the circle appears in the shape of a diamond, as illustrated in the second screen.

After pressing [ENTER] in this step, you can precisely locate the center by giving the calculator the coordinates of that point. You can also label the center.

3. Use the arrow keys to expand the circle to the desired size and press [ENTER] to anchor the size of the circle.

The third screen illustrates this step. The circle appears as dashed lines, indicating that the construction is not yet complete.

After pressing [ENTER] in this step, you can precisely locate the point on the circumference by giving the calculator the coordinates of that point. You can also label this.

4. Press [ENTER] or move the cursor away from the object.

This is a crucial step. If it is not followed, then the last circle you created may vanish when you ask GeoMaster to perform another operation. After doing this step, the circle which appeared as a dashed circle after performing Step 3 appears as a solid circle. This indicates that your construction is now housed in the memory of the calculator.

After constructing your first circle, the Circle tool remains active until you deactivate it. So if you want to construct more circles, just follow Steps 2 through 4. When you are finished using this tool, you deactivate it by pressing [CLEAR] or by selecting another menu item.

After a circle has been constructed, you can move its location on the screen by moving the circumference of the circle, and you can change the size of its radius by moving the point on the circumference of the circle.