FINDING THE AREA UNDER A CURVE
Graphmatica can perform numerical integration to find the area under the curve for any function on the screen. Just select Integrate from the Calculus menu. The cursor will change to the crosshairs. Now position the cursor over any point on a curve on the screen to select the function to integrate and the beginning bound of integration. Then click and drag the cursor along the x axis to highlight the interval you wish to evaluate and release the mouse button. (Using the keyboard, maneuver over the initial point, then hold down shift as you use the arrow keys to select the desired region.) To find the area between two curves, position the cursor over the second curve as you finish selecting the region.
The program will shade in the area that was found and display the numerical result in the status bar, as well as in the Printout window if you have it on. If you select a region under the axis, or highlight the region above the axis from right to left, you will get a negative area. The shading will be cleared as soon as you hide or delete the equation it belongs to, clear the screen, or perform another integration.
You can choose from several methods of integration, as well as specify how many segments to divide the region into, to select a more accurate computation or a more instructive graphic. You can also enter the curve(s) and the region using a dialog box for greater accuracy rather than using the mouse. See Integration Options for details.
Any integral shading you create will appear on the grid when you print or copy to a bitmap. Currently, there is no provision for saving or restoring integration regions, or for showing more than one shaded region at a time.