If you can see this red sentence, it means you aren't using a browser that can view Java programs, so you won't be able to use the calculator. Instructions:

Adding Functions

Press "Add Function" button and type in a formula to be graphed in standard mathematical notation (eg "e^(-x/10)sin(x)"). The only variable the formula can use is x. You can add as many functions as you like, and "Delete Function" deletes the last one you entered.

Rescaling

This brings up a panel which you can use to edit the scale of the graph. The x variable runs between xMin and xMax, and the y values run between yMin and yMax. Use xScale and yScale to set the spacing of tick marks on the axes. If xScale or yScale is zero, the graph will have no tickmarks on that axis.

Riemann Sums

Move the slider bar to vary the number of strips in the Riemann sums. The control buttons set whether or not to show the value of the Riemann sum in the screen, and whether to use left-hand or right-hand Riemann sums.