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IV.1.2: Editing: One advantage of the TI-89 is that you can use the arrow keys to scroll in order to see a
long calculation. For example, type this sum (Figure IV.4):
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Then press ENTER to see the answer. The sum is too long for both the entry line and the history area. The
direction(s) in which the line extends off the screen is indicated by an ellipsis at the end of the entry line and
arrows or in the history area. You can scroll through the entire calculation by using
or
to put
the cursor on the appropriate line and then using or to move the cursor to the part of the calculation that
you wish to see.
Figure IV.4: Home screen
Often we do not notice a mistake until we see how unreasonable an answer is. The TI-89 permits you to
redisplay an entire calculation, edit it easily, then execute the corrected calculation.
Suppose you had typed 12 34 56 as in Figure IV.5 but had not yet pressed ENTER, when you realize
that 34 should have been 74. Simply press as many times as necessary to move the blinking cursor line
until it is to the immediate right of the 3, press
to delete the 3, and then type 7. On the other hand if 34
should have been 384, move the cursor until it is between the 3 and the 4 and then type 8. If the 34 should
have been 3 only, move the cursor to the right of the 4, and press
to delete the 4.
Figure IV.5: Editing a calculation
Technology Tip: The TI-89 has two different inputting modes: insert and overtype. The default mode is
insert mode, in which the cursor is a blinking vertical line and new text will be inserted at the cursor’s
position and other characters are pushed to the right. In the overtype mode, the cursor is a blinking square
and the characters that you type replace the existing characters. To change from one mode to another, press
2nd INS. The TI-89 remains in whatever the last input mode was, even after being turned off.
IV-2
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TI-89 Graphics Calculator