Find the area of the largest rectangle that can be inscribed in the ellipse
All I have so far is that the area = 4xy
Not sure where to go next; too many variables.
Since the corners of the rectangle are on the ellipse, the "x" and "y" in xy must satisfy . As Unknown008 said, a and b are constants not variables. You can either write or differentiate xy with respect to x: y+ xy'= 0, and get y' by differentiating implicitely.