Olympic Stadium
Construction of this stadium requires determination of a circular area. 
Area of a Circle 

[ 4
wedges ]
[ 8 wedges ] [ 16 wedges ] [ Infinity ] 
To solve this problem,
we cut the original circle into a greater number of equal wedges. As we
increase the number, the bumps become smoother and the parallelogram looks
more and more like a rectangle. As the number approaches infinity, the
bumped "parallelogram" becomes a perfect rectangle, with its width equal
to r
and its height equal to r. As illustrated earlier, The width of this newly
formed rectangle equals half of the circumference of the original circle
and the height is equal to the radius r. As a result,
Area of Circle = Area of Rectangle = (r) r = r² 