Tech
This exploration into two circles requires a recent browser, version 4 at least, and uses four items of online interactive software Cinderella, JavaSketchPad. HotEqn and LiveMath.

Cinderella
This is interactive geometry written in Java, that should load automatically when you load the page. The use of Cinderella is central to this exploration, since it uses complex number theory to calculate coordinates of points. Most of the dynamic illustrations use Cinderella - particularly those showing the dual display of geometry and numerical data. According to the creators of Cinderella, these browsers will work:
Netscape Navigator/Communicator 4.06, 4.07, 4.08, 4.5 for Windows and Unix (not Macintosh), Netscape Navigator 4.5 with Java 1.1 patch, or Internet Explorer 4, 4.01, 5 (beta).
Cinderella homepage. Buy the software at

JavaSketchPad
This is also interactive geometry written in Java, that should load automatically when you load the page. JavaSketchpad homepage.

HotEqn
Some pages use step-by-step interactive algebra from HotEqn

LiveMath
This is interactive algebra which requires a plug-in to be installed on your computer. To do this, go to the MathsNet download page.