Abstract
The Cartesian ovals are simply defined with bipolar coordinates. However it is difficult to draw them by handwriting. In this paper, therefore, we have constructed a computational drawing system by means of XY plotter that works with PC 8001mkII. And then, the ovals will show some particular properties. First, the ovals change gradually with left and right eccentricities. Second, the set of the intersections of three circles forms the oval. Third, when the eccentricities change continuously without changing the director circle and the foci, the ovals fill between the ellipse and the director circle. Forth, there can be shown two kinds of evolutes of the ovals. The one is drawn as an evelope of the straight lines, and the other with paramatric equations. In this way, these properties of the oval can be shown for the first time by using computational drawing system.
