The square gets sent to a rectangle circumscribing the ellipse. Conjugate diameters in an ellipse generalize orthogonal diameters in a circle. These correspond respectively to the limiting forms of an ellipse, parabola, and a hyperbola. Define by the equations for an ellipse and for a hyperbola. There are three types of conics&colon; the ellipse, parabola, and hyperbola. The Moon's orbit approximates an ellipse rather than a circle. The four-line problem results in the ellipse and hyperbola. Eccentricity is defined as the difference in shape between an ellipse and a perfect circle. All tangent parallelograms for a given ellipse have the same area. The park is an ellipse bounded by Elliptical Road. Through any point of an ellipse there is a unique tangent. All closed orbits have the shape of an ellipse. It is sometimes useful to find the minimum bounding ellipse on a set of points. Eccentricity measures the departure of this ellipse from circularity. Circumference is used by some authors to denote the perimeter of an ellipse.