HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 57

The FCN menu, Root, Function Tools

Page 57 highlights

The FCN menu Note: Before continuing, set the axes back to the way we set them at the top of page 53. Looking at the menu functions again, you will see that the only one we have not yet examined is the one labeled . This key pops up the Function Tools FCN menu and is the most useful of them all. Before you use this key, make sure is switched on (ie showing ) and then move the cursor so that it is in roughly the position shown right. Root Press the key. As you can see on the right, this key gives you access to a number of useful tools. If you leave the highlight on Root (as shown) and press ENTER (or ) then the cursor will jump to the nearest root or x intercept for the function it is on, starting its search at the current position of the cursor. Try it now. Notice the message at the bottom of the screen giving the value of the root that was found. To find the other root, you need to move the cursor so that it is closer to the other root than to the present one. In this case that means moving it past the turning point. Move to about this position. Calculator Tip If you are working with a function which has asymptotes then make sure the cursor is positioned on the same side of the asymptote as the root. The internal algorithm used to find roots does not cope well with crossing asymptotes. 57

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The FCN menu
Note:
Before continuing, set the axes back to the way we set them at
the top of page 53.
Looking at the menu functions again, you will see that the only one we
have not yet examined is the one labeled
. This key pops up the
Function Tools
FCN
menu and is the most useful of them all.
Before you use this key, make sure
is switched on (ie showing
) and then move the cursor so that it is in roughly the position
shown right.
Root
key. As you can see on the right, this key gives you
access to a number of useful tools. If you leave the highlight on
Root
(as
shown) and press
ENTER
(or
Press the
) then the cursor will jump to the
nearest root or x intercept for the function it is on, starting its search at
the current position of the cursor. Try it now.
Notice the message at the bottom of the screen giving the value of the
root that was found. To find the other root, you need to move the cursor
so that it is closer to the other root than to the present one. In this case
that means moving it past the turning point.
Move to about this
position.
Calculator Tip
If you are working with a function which has asymptotes then make sure
the cursor is positioned on the same side of the asymptote as the root.
The internal algorithm used to find roots does not cope well with
crossing asymptotes.
57