iPhone now can be educational. iPlot is a software which can plot function graph. I am not good at math, so do not really know how to try it. But, this software may be useful to some of you. Add many function as you want, choose the color, and then save. Click Plot to draw the graph. You will be able to zoom in. Hope it will be useful for you. It can be found from Installer if you have installed Community Sources.