Texas Instruments TI-82 Manual page 11

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G T G : TI-82
RAPHING ECHNOLOGY UIDE
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Figure 2.27: Trace on y = –x + 4x
Press TRACE to enable the left ◄ and right ► arrow keys to move the cursor along the function. The cursor is no
longer free-moving, but is now constrained to the function. The coordinates that are displayed belong to points on
the function's graph, so the y-coordinate is the calculated value of the function at the corresponding x-coordinate.
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Now plot a second function, y = –.25x, along with y = –x + 4x. Press Y= and enter –.25x for Y , then press
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GRAPH.
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Figure 2.28: Two functions Figure 2.29: y = –x + 4x and y = –.25x
Note in Figure 2.28 that the equal signs next to Y and Y are both highlighted. This means both functions will be
1 2
graphed. In the Y= screen, move the cursor directly on top of the equal sign next to Y and press ENTER. This
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equal sign should no longer be highlighted (see Figure 2.30). Now press GRAPH and see that only Y
is plotted
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(Figure 2.31).
Figure 2.30: Y= screen with only Y active Figure 2.31: Graph of y = –.25x
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Many different functions may be stored in the Y= list and any combination of them may be graphed simultaneously.
You can make a function active or inactive for graphing by pressing ENTER on its equal sign to highlight (activate)
or remove the highlight (deactivate). Go back to the Y= screen and do what is needed in order to graph Y but not
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Y .
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Now activate Y again so that both graphs are plotted. Press TRACE and the cursor appears first on the graph of y =
2
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+ 4x because it is higher up in the Y= list. You know that the cursor is on this function, Y
–x , because of the
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numeral 1 that is displayed in the upper right corner of the window (see Figure 2.27). Press the up ▲ or down ▼
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