15: The condition that the rectangle is inscribed in the circle of radius
R means that the main diagonal of it must be the same as the diameter
of the circle.
The resulting equation
x2 + y2 = (2R)2
allows one to get rid of y.
The function
should be maximized over the set
M = [0,2R]
(the longest side of a rectangle in a circle cannot be longer than the
diameter).
Use the appropriate
algorithm.
