Texas Instruments TI-89 Manual page 23

TI-89 Guide
If you look closely, you can actually see the "hole" in the graph
−
at x = 1. Press
and the TI-89 confirms that u is not defined at x =
press and observe the y-value. Press
►
go to the left of x =
limit is approximately what we had determined numerically.
Note that we confirmed that the limit exists by seeing that the two parts of the graph (to the left
−
and right of x =
numerical value of the limit.
The previous instructions show how to zoom in by manually setting the window. You can
also zoom in with the zoom menu of the calculator. We next describe this method.
Return to the graphing screen set with
F2 [Zoom] 6 [ZoomStd]
portion of the graph around x =
and use
In] ◄
near the point on the graph where x =
Depending on the horizontal view, you may or may not be able
to see the hole in the graph at x =
fied enough to see what is happening around x =
zoom-in process. To check your numerical estimate of the limit,
press
F3 [Trace]
−
= 1, and observe the y-values.
Now let's consider the limit in part b of Example 2 of Section 1.4. We want to confirm with a
graph what was found numerically; that is, we wish to confirm that
We want to zoom out on the graph to confirm that the limit of
u(x) as x approaches
small x-view and a larger y-view. (Note that these values are
arbitrary – any small x-view that includes
which the graph can be seen clearly will do.)
Draw the graph with
the limit investigation, we need to eliminate the "extra" vertical
line that appears on the above graph at x =
because we are graphing in
connect points on the graph. (You may or may not have the line
on your graph.)
Set set to draw in
y 1
2nd F1 [F6: Style] 2 [Dot].
(GRAPH).
Copyright © Houghton Mifflin Company. All rights reserved.
, use ► to trace to where x =
F3 [Trace]
−
1 and confirm from the y-values that the
1) move toward the same point. Tracing around x =
or any screen where you can see the
−
1.) Press
and to move the blinking cursor until you are
▲
−
−
1. If your view is not magni-
, use the arrow keys to move to either side of x
−
2/9 does not exist. To do this, we set a
F3 (GRAPH).
mode, which tells the TI-89 to
Line
mode by highlighting
Dot
Redraw the graph with
−
1,
−
1. Now
◄
several times to
F2 [Zoom] 4 [ZoomDec]
F2 [Zoom] 2 [Zoom
1. Press
ENTER .
−
1, repeat the
−
2/9 and any y-view in
Before continuing with
−
2/9. The line appears
and pressing
y 1
F3
TI 89-23
−
1 provides a check on the
or
lim
u(x) does not exist.
−
x→ 2/9