Given a Math function formula, one could study the function properties by drawing graph on the paper by hand. It usually takes four steps. First is to choose different x values of the function. Second is to calculate the corresponding y values from the x values. Third is to draw pairs of points (x,f(x)) on the paper. Forth is to draw lines between adjacent points. It may be easy to plot a graph of simple functions like f(x)=2x. However, it may take more than 10 minutes to figure out how to plot the graph of trigonometric functions like f(x,y)=sin(x+y) or f(x,y)=sin((x/4)^2+(y/4)^2. Moreover, no one can guarantee the accuracy of the hand-plotted graph. The XPlot provides solutions to you. You need XPlot to replace the pencil and the paper with the keyboard, mouse and computer screen to plot the graph. The graph plotted is interactive. Change of point of views, zoom in and zoom out, adjust the plot range, and colorize the graph are all made possible in XPlot. http://sourceforge.net/projects/mathdev/ http://freshmeat.net/projects/xplot/