Riemann+Sum+Definition

The Riemann sum is basic in that the length of the rectangle can either be the leftmost coordinate point, the rightmost coordinate point, or the midpoint of the two coordinate points. Multiplying length by the height of the rectangle will provide the area of a rectangle. Add the areas of all the rectangles in order to produce the estimated sum. The median Riemann sum is the most accurate as a left Riemann sum is too low when the function is increasing and too high when the function is decreasing, wheras the right Riemann sum is too high when the function is increasing and too low when the function is decreasing.