Texas Instruments TI-85 - Manual (Page 9)

Chapter 1 B-9
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Estimate the value of A where A = 1000(1 + 0.05) x
when x = 5 , x = 7 , and x = 10 .
Press EXIT F2 ( RANGE ) (or WINDOW ) . If you do not
have the settings shown to the right, reset the values.
Press F3 ( ZOOM ) F3 ( ZOUT ) . After the graph
finishes drawing, press ENTER to once more
enlarge your view of the graph.
(Press EXIT F2 ( RANGE ) and observe the values
now defining the graphics screen.)
Note that (5, 1450) is a point
on the screen, not a point on the
graph of the function.
Press F4 ( TRACE ) and use to move as close as you
can to x = 5. (Your screen may look slightly different
than the one shown to the right.)
Continue pressing and notice that the values 7 and
10 cannot be obtained by tracing in this view. Therefore,
choose values close to these numbers to obtain estimates
such as A is approximately $1386.80 when x = 7 and A
is about $1637.37 when x = 10.
Because the number 5, not a
value close to 5 is shown,
A = $1276.28 when x = 5.
¥ If you had used the original range (window) with xMax = 10 , and traced, you should
obtain the exact value A = 1500 when x = 10 because 10, not a value close to 10, is shown
when tracing.
¥ If you want Ònice, friendlyÓ values displayed for x when tracing, set xMin and xMax so
that xMax
-
xMin is a multiple of 12.6, the width of the ZDECM viewing screen. For
instance, if you set xMin = 0 and xMax = 12.6 in the example above, the exact values when
x = 5 , x = 7 , and x = 10 are displayed when you trace. Another view that gives friendly
values is xMin = – 5 and xMax = 20.2 since 25.2 = 2(12.6). Try it!
1.1.7 EVALUATING OUTPUTS The values obtained by this evaluation process are
actual output values of the equation, not estimated values such as those generally obtained
by tracing.
Begin by entering the equation whose output you want to evaluate in the y(x)= list.
Even though you can use any of the locations, let us say for this illustration you have
y1 = 1000(1 + 0.05^ x ).
To evaluate an output while the graph is on the screen:
Draw the graph of y1 in a view containing the input
you intend to use. (If the input value is not between
xMin and xMax , an error message results when you
evaluate.)
Press MORE MORE F1 ( EVAL ) , and type the input value.