Consider the ellipse `E_1, x^2/a^2+y^2/b^2=1,(a>b)`. An ellipse `E_2` passes through the extremities of the major axis of `E_1` and has its foci at the ends of its minor axis.Consider the following property:Sum of focal distances of any point on an ellipse is equal to its major axis. Equation of `E_2` is