Software for Geometric drawing

Yesterday, while doing some work on my thesis, I needed to draw a geometric shape to determine three points on a circle which contains a triangle inside. I needed those three points to be the location of three wireless nodes. As I do not have compasses, protractor (চাঁদা!) or anything of that sort with me (who does after the school days!?), it was kind of troublesome. I searched in Google for this and came to know about this software, cleverly named C.a.R - which means "Compass and Ruler" or "Construct and Rule". Though it takes some time in the beginning to have a grasp of the things, after that initial part it is quite easy to use. Here is the link of the program homepage : http://zirkel.sourceforge.net/

The software is open source, runs on any platform (needs Java), and is a small download.

I have got my three points, now back to work!