Note that the TI-86 and the TI-85 have slightly different keys. This page uses the keys associated with the TI-86. The differences are in the "2nd" functions on some of the keys used here. The TI-85 keys will have the same key-face symbol unless otherwise noted. |
This page looks at Example 16 from Chapter 1 Section 2. The problem in that example is
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We start entering the inequality on the "y=" screen. The
![]() ![]() ![]() ![]() ![]()
The next character that we need to enter is the "less than or equal to" character.
To do this we will open the TEST menu via
the |
![]() | ![]() ![]() ![]() ![]() ![]() ![]() ![]() At this point we want to continue the inequality with "and". We could actually type the word, being careful to do so in lower case letters, but it might be easier to find "and" in the CATALOG. |
![]() | In Figure 3 we have opened the CATALOG via the
![]() ![]() ![]() |
![]() | The CATALOG on this calculator opened at the top of its list.
(Had the CATALOG opened at some other point we could have
pressed the ![]() |
![]() | We press the ![]() ![]() |
![]() | Note that after our use of the CATALOG we have been returned to the "y=" screen and that "and" has been pasted into our expression. Now we are ready to complete our problem. |
![]() | ![]() ![]() ![]() ![]() ![]() ![]() |
![]() | To complete the line we press
![]() ![]() ![]() ![]() ![]() |
![]() | The ![]() ![]() ![]() |
![]() | Figure 10 demonstates the solution, the half-closed, half-opened
interval |
As noted on other web pages, the graph shown above, although correct and although it does a good job of showing where the inequality is TRUE, does not do a good job of showing where the inequality is FALSE. This is so because the value FALSE is associated with 0 on the TI-86 and as the calculator plots those 0 values the graph is on top of the x-axis. Therefore, we do not see any change to the graph as the 0 values are plotted. The scheme that we have used before to emphasize the TRUE and FALSE values is to multiply the entire inequality by 3 and then subtracting 1. As a result, TRUE is plotted as 2 while FALSE is plotted as 1. The following images show the conversion of the formula and the resulting graph.
![]() | In Figure 11, the
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![]() | ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
![]() | Knowing that our function will produce either 2 or 1
we can narrow the range of Y values by using the
![]() ![]() |
![]() | For Figure 14 we have used the cursor keys to move around in the
screen and we have changed the yMin and yMax values.
Pressing the ![]() |
![]() | Here the graph is drawn. Now it is easier to see both the TRUE and the FALSE regions. |
PRECALCULUS: College Algebra and Trigonometry
© 2000 Dennis Bila, James Egan, Roger Palay