Texas Instruments TI-83 PLUS - Manual (Page 586)

TI-83 Plus Activities 583
7. Press † to move to the path of the ball. Notice the values of X and Y
( T is unchanged). Notice where the cursor is located. This is the
position of the ball when the ferris wheel passenger passes the
intersection. Did the ball or the passenger reach the intersection first?
You can use r to, in effect, take snapshots in time and explore
the relative behavior of two objects in motion.