Texas Instruments TI-82 Manual page 7

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RAPHING

ECHNOLOGY

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Technology Tip: If you would like to see a function in the Y= menu and its graph in a graph window, both at the

same time, open the MODE menu, move the cursor down to the last line, and select Split screen. Your TI-82's

screen is now divided horizontally (see Figure 2.11), with an upper graph window and a lower window that can

display the home screen or an editing screen. The split screen is also useful when you need to do some calculations

as you trace along a graph. For now, restore the TI-82 to FullScreen.

Your graph window may look like the one in Figure 2.12 or it may be different. Since the graph of y = –x

+ 4x

extends infinitely far left and right and also infinitely far up and down, the TI-82 can display only a piece of the

actual graph. This displayed rectangular part is called a viewing rectangle. You can easily change the viewing

rectangle to enhance your investigation of a graph.

Figure 2.11: Split screen: Y= below

Figure 2.12: Graph of y = –x

+ 4x

The viewing rectangle in Figure 2.12 shows the part of the graph that extends horizontally from –10 to 10 and

vertically from –10 to 10. Press WINDOW to see information about your viewing rectangle. Figure 2.13 shows the

WINDOW screen that corresponds to the viewing rectangle in Figure 2.12. This is the standard viewing rectangle

for the TI-82.

Figure 2.13: Standard WINDOW

The variables Xmin and Xmax are the minimum and maximum x-values of the viewing rectangle; Ymin and Ymax

are its minimum and maximum y-values.

Xscl and Yscl set the spacing between tick marks on the axes.

Use the arrow keys ▲ and ▼ to move up and down from one line to another in this list; pressing the ENTER key

will move down the list. Press CLEAR to delete the current value and then enter a new value. You may also edit the

entry as you would edit an expression. Remember that a minimum must be less than the corresponding maximum or

the TI-82 will issue an error message. Also, remember to use the (-) key, not – (which is subtraction), when you

want to enter a negative value. Figures 2.12–13, 2.14–15, and 2.16–17 show different WINDOW screens and the

corresponding viewing rectangle for each one.