Download MS Maths, its free

It solves, draws graphs, solves triangles, etc

You know it has so many features that during my pre-calculus, calculus and physics refresher I never once had to use anything else.

http://www.microsoft.com/en-us/download/details.aspx?id=15702

Ok, I'm liking this a lot at first sight.

Too bad it only has a triangle solver, but not really the ability to sketch and measure lines and polygonal data in general, though :(