This forum has very little traffic, and very low upload limits for files. The main Mathcad forum is here: http://collab.mathsoft.com/~mathcad2000 You should go there, and post a worksheet showing where you have got to. If you save back to version 11 format you will get a wider audience. You will need to plot it parametrically, but it's hard to explain how to do that without putting it in a worksheet. Richard
