This applet draws a parametric curve [x(t),y(t)], for t in a specified range (unfortunately this range is not shown in the applet, you have to look at the html source) of values. It does this by plotting a sequence of points on the curve and connecting them with lines. The number of points that are plotted can be controlled (also in the html). There is a "Trace Curve!" button. If you click this button, a crosshair will move along the curve.