Math Mechanixs 1.2.0.1 is a free program to use in scientific works (it requires free registration to continue working after 30 days) and comes integrated with a scientific calculator, and a maths editor that allows complex calculations while it offers you details on the work you´re doing.
You can save the analysis of your work, and have over 200 more predefined functions, a generator of 45 different statistics, and 3D or 2D graphical representations.