A very brief discussion about the creation of these pictures is available. Here are some methods for displaying the calculus exercise:
In postscript and in pdf .
The postscript file is sharp and lovely -- but not many browsers can "read" it. The pdf format is generally readable. The pdf file is converted from postscript, and doesn't look as good to me. Both of these files are considerably larger than the gif file, and take a while to load along slower net connections.
You may also want to consider the various TeX-to-gif translators, which basically create many small gif's for each TeX expression. One such is mentioned on the previous page, under Alternatives.
As one huge gif (the file is small, so downloading is faster and just about every browser can handle gifs, but the image is very fuzzy):