DEVICE AND METHOD FOR DRAWING TILTED ELLIPSE SIMULTANEOUSLY TOUCHING TWO STRAIGHT LINES ON DISPLAY SCREEN AND RECORDING MEDIUM WITH PROGRAM DRAWING THE ELLIPSE RECORDED THEREIN

PROBLEM TO BE SOLVED: To easily and accurately draw a tilted ellipse which simultaneously touches two optional straight lines on a display screen by means of a computer. SOLUTION: The following processes are executed by a computer. That is, two points are designated on each of two straight lines on a display screen (S1). The point of contact between a tilted ellipse and one of both straight lines is designated, together with a point of contact between the tilted ellipse and the other straight line (S2, S3). A single point is designated on the tilted ellipse, excluding two points of contact (S4). The equation for a secondary curve is obtained, based on the position coordinates of two points set on each of two straight lines, the position coordinates of two points of contact and the position coordinates of the single point (S5). When the equation represents an ellipse (S6), the position coordinates of every point set on the tilted ellipse is calculated by the equation (S7). Then the tilted ellipse is drawn on the display screen, based on the position coordinates which are calculated by the equation (S8).