HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 75

Integration: The definite integral using PLOT variables As was discussed earlier, when you find roots, intersections, extrema or signed areas in the PLOT view, the results are stored into variables for later use. For example, if we use Root to find the x intercept of f (x) = x2 − 2 then the result is stored into a variable called Root, which can be accessed anywhere else. Similar variables called Isect, Area, and Extremum are stored for the other tools. You can access these names by typing them in using the ALPHA key, or by using the VARS key. Press VARS and you will see a list of the HOME variables. If you press SK2, labeled (not the APLET button on the keyboard), then the display changes to show the variables specific to whatever aplet you are currently using. Those shown right are for the Function aplet and the group of Plot FCN variables is shown. If you look at the screen shot you will see that the tag is currently selected (showing as ) and this means that when you press the name of the variable will be pasted into what ever view you were using when you pressed the VARS key. Pressing the screen key will cause the value of the variable to be pasted instead. There is no effective difference in most situations. This can be very useful in finding areas, as you will see in the example on the following page. 75