geogebra

**GeoGebra** is a (Java-based) free software for graphing, algebra, geometry and statistics suited for educational use. Graphs in GeoGebra may have adjustable parameters, for example points of geometrical figures which can be changed with mouse, and the dependent parts of the graphs will change along (for example, in an image of a triangle with its orthocenter constructed we can change the vertices of the triangle and the orthocenter will change along in real time).

GeoGebra appears in desktop versions in several major operative systems (including Linux) and in the online web version which can be directly used online. The web version is hosted along with a large database of shared files which implement many tasks or educational demonstrations in GeoGebra. The desktop version has the option to export the graphs to various portable formats, e.g. SVG. Of course, the exported images are static (no graph parameters can be changed).

- geogebra.org
- Wikipedia: geogebra