Construct Circles in Cabri Jr. on the TI84 Plus
You can use the Cabri Jr. geometry application on the TI84 Plus to construct circles. A circle is determined by entering its center and its radius. To construct a circle, follow these steps:

Select the Circle tool from the F2 menu.
To do this, press [WINDOW][4]. A picture of a circle appears in the upper left of the screen indicating that the circle tool is active.

Use the arrow keys to move the cursor to the location on the screen where you wish to place the center of the circle. Press [ENTER] to anchor this point.
The center of the circle appears as a flickering point, indicating that the circle is not yet constructed. This is illustrated in the first picture, although the picture, of course, cannot display a flickering point.

Use the arrow keys to expand the circle to the desired size.
As you use the arrow keys to move the cursor, the radius of the circle expands and the circle is displayed as a dotted circle, indicating that the construction is not yet complete. This is illustrated in the second picture.
After using the arrow keys to expand the radius of the circle, you can, using the arrow keys, move the cursor in the opposite direction to contract the size of the radius.

When the circle is as you want it, press [ENTER] to complete the constructing of the circle.
The circle appears as solid lines, indicating that the construction is complete. Also, a point appears on the circumference of the circle at the location of the cursor. This is illustrated in the third picture, where the cursor has been moved away from the circle.
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.
After constructing your first circle, the Circle tool remains active until you deactivate it. So if you want to construct more circles, just repeat Steps 2 through 4. When you are finished using this tool, you deactivate it by pressing [CLEAR] or by selecting another menu item.