TI-83, TI-83 Plus, TI-84 Plus Guide
Press
ENTER and the input value is substituted in the function.
The input and output values are shown at the bottom of the
screen. (This method works even if you do not see any of the
graph on the screen.)
Substitute the right endpoint of the input interval into the
function by pressing
20 ENTER .
We see that two points on this function are approximately
(0, 3.5) and (20, 21.496).
Press WINDOW , enter 3.5 for Ymin and 22 for Ymax, and press
GRAPH . If the graph you obtain is not a good view of the
function, repeat the above process using x-values in between the
two endpoints to see if the output range should be extended in
either direction. (Note that the choice of the values 3.5 and 22
was arbitrary. Any values close to the outputs in the points you
find are also acceptable.)
NOTE: Instead of using TRACE with the exact input to evaluate outputs on the graphics
screen, you could use the
TABLE function or evaluate the function at 0 and 20 on the home
screen. We next discuss using these features.
TRACING TO ESTIMATE OUTPUTS You can display the coordinates of certain points
on the graph by tracing. Unlike the substitution feature of
TRACE that was discussed on the
previous page, the x-values that you see when tracing the graph depend on the horizontal view
that you choose. The output values that are displayed at the bottom of the screen are calculated
by substituting the x-values into the equation that is being graphed. We again assume that you
have the function v(x) = 3.5(1.095
x
) entered in the Y1 location of the Y= list.
With the graph on the screen, press TRACE , press and hold
► to move the trace cursor to the right, and press and hold
◄ to move the trace cursor to the left. The equation that you
are tracing appears at the top of the graphing screen.
Trace past one edge of the screen and notice that even though
you cannot see the trace cursor, the x- and y-values of points
on the line are still displayed at the bottom of the screen. Also
note that the graph scrolls to the left or right as you move the
cursor past the edge of the current viewing screen.
Use either ► or ◄ to move the cursor near x = 15. We
estimate that y is approximately 13.9 when x is about 15.
It is important to realize that trace outputs should never be
given as answers to a problem unless the displayed x-value is
identically the same as the value of the input variable.
Copyright © Houghton Mifflin Company. All rights reserved.
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