Plots have been used to illustrate mathematical concepts from the time of Rene Descarte who indroduce Cartisian coordinates. A static printed plot is of great use, but a dynamic plot which can be changed with the mouse is now possible on a web page.
Java is a natural language for writing these interactive plots. Here we have 6 examples. Each example comes in several versions. The first version is always the simplest plot. In some cases there is a progression with the final version being the one that "corrects" the problems in the earlier examples. In oher case, each example stands on it's own and just shows another way to illustrate the concept.