We can edit an expression without starting again. If we place the cursor over a symbol and press a new key, the new symbol replaces (overwrites) the old one.
ExampleB.24.
Correct the error in the following keystrokes for \(120 - 36\text{:}\)
\(\qquad\qquad 120\)(-)\(36\)ENTER
The calculator gives an error message (See Figure B.23.) Select "2:Goto", and a blinking cursor appears over the error. Press - to replace the negative symbol by the subtraction symbol.
SubsectionRecalling an Entry
We can recall a previous entry by pressing 2ndENTER.
ExampleB.25.
Evaluate \(\sqrt{3}+\sqrt{2}~~ \) and \(~~\sqrt{3}-\sqrt{2} \text{.}\) First evaluate \(\sqrt{3}+\sqrt{2} \text{:}\)
2ndx^2)+2ndx^2\(2\)ENTER
Ans. \(3.14626437\)
Now press 2ndENTER to recall the last entry, and use the left arrow key ← to position the cursor over \(+\text{.}\) Press - to change to \({}-{}\text{,}\) then press ENTER. Your screen should look like Figure B.26.
FigureB.26.
SubsectionInserting a Character
To insert a new character before a symbol, position the cursor over that symbol and press 2ndDEL to get the INS (insert) command.
ExampleB.27.
Evaluate \(\sqrt{3}-5\sqrt{2} \) by editing the example above.
Press 2ndENTER to recall the last entry, and use the left arrow key ← to position the cursor over the second \(\sqrt{\,}\) from left to right. Press 2ndDEL\(5\) to insert 5 before the \(\sqrt{\,}\) symbol, then press ENTER. Your screen should look like Figure B.28.
FigureB.28.
SubsectionRecalling an Answer
We often want to use the result from a previous calculation in a new calculation, without having to type in the number. We use the ANS key, 2nd(-), to recall the answer to the last calculation.
ExampleB.29.
Evaluate \(\sqrt{5}-1 \)
2ndx^2\(5\))-\(1 \)ENTER
Ans. \(1.236067977\)
Evaluate \(x^2 + 2x + 1\) for \(x = \sqrt{5}-1 \text{.}\) Because \(x\) is the last answer the calculator computed, we enter
