Use the Coord. & Eq. Tool in Cabri Jr.
The Coord. & Eq. tool in the Appearance menu of Cabri Jr. on the TI84 Plus is used to find the equation of an already constructed line or circle or to find the coordinates of a point appearing on the screen.
To find the equation of a line or circle or the coordinates of a point, follow these steps:

Press [GRAPH] to select the Appearance menu. Use the
keys to place the cursor on the Coord. & Eq. option and press [ENTER] to select that option.
A symbol of the Coord. & Eq. tool appears in the upperleft corner of the screen.

Use the arrow keys to move the cursor to the object whose equation or coordinates you want to find and press [ENTER].
The object blinks when the cursor is placed on it. After pressing [ENTER], the equation or coordinates appear at the location of the cursor.

Use the arrow keys to move the equation or coordinates to a better location and press [ENTER] to anchor that location.

Repeat Steps 2 and 3 to find the equation of another line or circle or the coordinates of another point. When you are finished finding equations and coordinates, press [CLEAR] or select another menu item.
After you have found the equation of a line or circle or the coordinates of a point, you can move the object and watch the equation or coordinates change accordingly. This is illustrated in the third picture, where the line is moved.