don't know if this was posted here before, or exactally how common this program is, but for doing anykind of mathamatical problems, it is probably the best out there...
you can plot graphs, differenciate/integrate them (at a certain point), get rates of change...and the list goes on, so i better stop, so i don't start sounding like an advertisement.


maple is one cool tool.


http://www.maplesoft.com