Integrator
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Integrator Applet to find right, left, and general Riemann sum as well as
upper and lower sums.
 Click on Options to bring up a dialog window for options
 For a definition of Riemann Sum, click
here.
 For a definition of upper and lower sum, click
here.
 For a definition of Riemann integral, click
here.
Also check the
general introduction to the Riemann integral
as well as a discussion of various
integration techniques.

You may also want to learn more about the
Lebesgue integral, a generalization of the
Riemann integral.