In a message dated 97-09-14 18:20:39 EDT, you write:
<< I agree with Bob that my method of finding differences is not the best.
Its only advantage is simplicity; I can avoid distructions when the most
obvious method is used. And in the problem at hands this method does give
perfect results when t and d data are perfect, even when time increments
are not very small. But this would not be good for many other problems.
>>
Ludwik,
If understanding the finite derivative is a problem for students, you might
try this approach. Draw a quarter circle on the board. Label the end points
A and C, and the mid point B. Draw straight line segments from A to B, A to
C, and B to C. Then draw a tangent line through B. Ask your students which
line segment more accurately represents the tangent line through B.