I recently came across this open source cross-platform application which is a dynamic maths software package. Absolutely magic! If only I’d had this when preparing for exams all those years ago. It combines graphic ingenuity with formulas and modelling. If you are preparing for exams or even just curious about maths, algebra, geometry or basic calculus then do take a look at this.
The home page is here and there are loads of tutorials and examples to help get you started.