Answer:
Ellipses are required in engineering, architectural, and machine drawings for two main reasons. First, any circle viewed at an angle will appear to be an ellipse. Second, ellipses were common architectural elements, often used in ceilings, staircases, and windows.
The ellipse is one of the four classic conic sections created by slicing a cone with a plane. The others are the parabola, the circle, and the hyperbola. The ellipse is vitally important in astronomy as celestial objects in periodic orbits around other celestial objects all trace out ellipses.