ZGrapher 1.4 (last freeware version) is an awards winning graphing and calculating software. With ZGrapher you can create and explore graphs of y(x), x(y), polar, parametric and table defined functions. All your graphs and coordinate space may be fully customized. You can place your comments using labels and legend.
The program has calculus capabilities. For a few seconds you can find derivatives, tangents, normals and calculate integrals. With help of regression analysis feature you can find trend of your data.
Results of your work may be exported to Word or saved as BMP, GIF and PCX pictures.