HP 39gs Quick Start Manual page 15

The HP 39gs uses the current cursor location for tasks such as finding roots, intersections, and slope at a
point. To find the best numerical approximation to the root, press the MENU key to restore the menu, press
the FCN menu key to see the list of options, and select the ROOT command (Figure 20). Press the OK menu
key. The result, accurate to 12 digits, is shown in Figure 21.
Let's find the intersection of the two graphs at (4, - 1 ). With the cursor at its current location at the root, return
to the menu, press the FCN menu key, select the Intersection option, and press the OK menu key. The HP
39gs uses the current function being traced as one of the curves involved in the intersection; you must
choose the other curve from a list, as shown in Figure 22. All active graphs, as well as the x-axis, are
included in this list. With F2(X) highlighted as in Figure 22, press the OK menu key. The results are shown
in Figure 23, in which the intersection found at (4, - 1 ) is displayed.
Figure 20
Figure 21
Figure 22
Getting Started 9