Compare Reimann Sums
This is a fast applet to compare the effectiveness of various methods of Riemann sums.
You can change the function and the number of subintervals.
It should be noted that the left and right hand rules are exact for constant functions.
The midpoint and trapezoid rules are exact for linear functions.
Simpson's rule is exact for cubic functions.
In general you should not how much the error is diminished by doubling the number of intervals.