The slider for h is non-linear so that when h is near zero it can be set precisely enough on the slider to get good approximations (six significant digits) to the average velocity at a. Note what happens when h = 0.

Students should investigate the behavior of the averagevelocity at each of the points a = 1, 2, 3, 4 by using the slider tolet h -> 0. A technical suggestion: use the slider to get h close to zero. Then usethe arrows at the end of the slider bar to make the final approach to zero.

The RESET button is only for purposes of starting over if desired. Anon-screen applet will remain active as long as the page containing it isactive. Sometimes the student may want to do the exercise twice. Or anotherstudent looking over her shoulder might want to try it.