Simple minimax example. The slider controls the horizontal length of the rectangle: a. The height of the rectangle is 10 -a Therefore the perimeter of the rectangle is fixed as 20. As the slider is moved the horizontal and vertical lengths change and hence the areas change. Also shown is the value of the area plotted against the horizontal length. How do you read the graph? Does the shape of the graph indicate that there is a maximum or minimum area? What is the shape of the rectangle when the area is maximum?