We have the formula for determing the area of an ellipse : a = Pi * x * y, and we have to find the equivalent equation solved for y. In this formula x is half the length of the largest and y is half the length of the smallest diameter of the ellipse. Pi is approx. 3.14. Starting with: a = Pi * x * y ( we will divide both sides of the equation by: Pi * x ) => a /(Pi*x) = y. Answer: y = a / (Pi*x).