Eigenmath is a freeware computer algebra application for windows and Mac.
This tiny application (569kb) has a very user friendly interface. You can insert an equation, draw graph, differentiate or integrate it, by using simple commands. For example:
1) insert your equation by typing "y=2*x"
2) draw it's graph "draw(y)"
3) integrate "integral(y)"
4) differentiate "derivative(y)"
Now you will be able to see on your screen, a graph of "y=2*x", it's integral "x2" and the derivative "2". Eigenmath supports a lot of commands which are explained in a simple manual. You can also create and edit scripts, using "run script" and "edit script" buttons.
Just download "eigenmath137.exe" file and run it. Windows may block the program because it can't find program's publisher. We tested this application and found it safe to unblock and run it.
Enjoy!