On this page, you can vary the number of partitions, N, used to approximate the area of the region bounded above by the graph of y = f(x), below by the x-axis, and vertically by the lines x = a and x = b. Submit real values for all of the parameters to obtain a numeric approximation of the area, the error involved, and a visualization of the region with the rectangles used. On this page, the height of the rectangles is determined by utilizing the x-value of the middle of each subinterval.