Geogebra is a free and multi-platform dynamic mathematics software

[johndb]

Geogebra is a free and multi-platform dynamic mathematics software for learning and teaching. Looks pretty good to me if you can't afford an advanced software program like Mathematica or Matlab.

 

[Sankaku]

I like Geogebra: cross platform, great fun for showing stuff to kids. Even does some very basic calc. Decent for quickly slapping together diagrams for other documents.
http://en.wikipedia.org/wiki/Geogebra

However, if you want an alternative to Mathematica, look at Maxima instead.
http://en.wikipedia.org/wiki/Maxima_(software)

Matlab has a few FOSS clones:
http://en.wikipedia.org/wiki/Scilab
http://en.wikipedia.org/wiki/GNU_Octave

Three very different problems need three very different types of program...

 

[oswaler]

I can attest to the usefulness of Geogebra in the field of mathematics. Not only is it a free software, but its multi-platform capabilities make it accessible to a wide range of users. Additionally, its dynamic nature allows for interactive learning and teaching, making it a valuable tool for both students and educators. While it may not have all the advanced features of programs like Mathematica or Matlab, Geogebra still offers a robust set of tools for mathematical exploration and analysis. Overall, I agree that Geogebra is a valuable resource for those who may not have access to more expensive software programs.