GeoGebra is a powerful mathematics tool for everybody, who is concerned with geometry. This program allows you to build drawings of almost any complexity.
You can add points, lines, vectors, polygons, circles, angles, text and even images from files (.gif, .jpg, .png, .tiff) to your drawings. All objects have bindings to coordinates. So you may get to learn various information like distance or length, area, angle, equation. Besides standard figures, there are many additional elements for editing (parallel line, semicircle, locus, mirror at line, bisector, etc.). Every element can be changed dynamically afterwards. Just type-in an equation in the form and the element will be added ('(x-3)^2+(y-5)^2=100' for the circle). The program has a very user friendly and beautiful interface and, what is more, it is absolutely free. GeoGebra is very fast, and works steadily. You may export the resulting image as a picture or save it on the disk in a special format. Also you can print your drawing (with scale mark) out.
It doesn't seems what it is ........ ***** 5 of 5 stars #geogebra
When I download it .. I can't open it!
I've used this for 10 years. It's very useful.