ABSTRACT
A baseball pitcher throws a fastball across home plate. The batter, following time-honored advice, tries to keep his eye on the ball. (Note that the exact same situation occurs in tennis, softball, and other sports.) The ball, batter’s eye, and the middle of home plate form a triangle that changes as the ball moves toward home plate. Assuming that the batter stands 2 feet from the plate, viewed from above the triangle looks like Figure 3.1.
