Editing Expressions / 31
Editing Expressions
Changing a Name or Number
To edit a name or number:
1.Click on it. The blue insertion line appears.
2.Move the blue insertion line by pressing the left and right arrow keys.
3.If you type a character, it appears just to the left of the blue insertion line. Pressing [Backspace] removes the character to the left. Pressing [Delete] removes the character to the right.
Inserting an Operator
The easiest place to insert an operator is between two characters in a name or two numbers in a constant. To insert a plus sign between two characters:
1. Place the editing lines where you want the plus sign to be.
2. Press the [+] key, or click 
on the Calculator toolbar.
Note Mathcad inserts spaces automatically around operators when needed. If you press [Space] in a math region, Mathcad assumes you meant to type text rather than math and converts your math region into a text region or moves the blue editing lines to enclose more of an expression.
When you insert a division sign, Mathcad moves everything that comes after the division sign into the denominator. To insert a division sign:
1. Click in the expression.
2. Press the [/] key or click |
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on the Calculator toolbar. Mathcad reformats |
the expression. |
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Some operators require only one operand, such as the square root, absolute value, and complex conjugate operators. To insert one of these, place the blue insertion line on either side of the operand and press the keystroke or button from a math toolbar. For
example, to turn x into
x :
1. Click next to the x, either preceding or following the character.
2.Press [\] to insert the square root operator or click 
on the Calculator toolbar.
Applying an Operator to an Expression
If you want to apply an operator to an entire expression:
•Surround the expression in parentheses, or
•Use the editing lines to specify the expression.
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Although the first method may be more intuitive, it is slower since you need to type a pair of parentheses. See “Inserting Parentheses” on page 33.
The editing lines consist of a horizontal blue underline and a vertical blue insertion line that moves left to right along the blue underline. To make an operator apply to an expression, select the expression by placing it between the two editing lines. The following examples show how typing *c results in different changes depending on what you select first.
•The two editing lines hold only the numerator. Any operator you type applies only to the numerator.
•Typing *c applies the operation to the numerator only.
•The editing lines hold the entire fraction. Any operator you type applies to the entire fraction.
•*c applies to the whole fraction.
•The editing lines hold the entire fraction.
•Typing *c puts the c before the fraction because the blue insertion line was on the left side.
Deleting an Operator
To delete an operator that connects two variable names or constants:
1. Click after the operator.
2.Press [Backspace], or if the blue insertion line was before the operator, press [Delete].
You can then insert a new operator just by typing it in.
Fractions behave the same way. Since we naturally say “a over b,” putting the editing lines “after” the division bar means putting them just before the b.
Here’s an example:
1. Place the vertical editing lines after the division bar.
2. Press [Backspace].
Editing Expressions / 33
To delete an operator having only one operand (for example, 
x , x or x! ):
1. Position the editing lines just after the operator.
2. Press [Backspace].
For certain operators, it may not be clear where to put the editing lines. For example,
it is not clear when looking at x or x what “before” and “after” mean. Mathcad resolves this ambiguity by using the spoken form of the expression. For example, since
you read x as “x conjugate,” the bar is treated as being after the x.
Replacing an Operator
To replace an operator after deleting it, simply type the new operator. To replace an operator between two expressions:
1.Position the editing lines just after the operator.
2.Press [Backspace]. An operator placeholder appears.
3.Type the new operator.
Inserting a Minus Sign
The minus sign that means “negation” uses the same keystroke as the one that means “subtract.” To determine which one to insert, Mathcad looks at where the blue insertion line is. If it’s on the left, Mathcad inserts the “negation” minus sign. If it’s on the right, Mathcad inserts the “subtract” minus sign. To move the blue insertion line from one side of the blue underline to the other, use [Insert].
The following example shows how to insert a minus sign in front of “sin(a).”
1.Click on the sin(a). If necessary, press [Space] to select the entire expression.
2.Press [Insert] to move the vertical editing line all the way to the left.
3. Type [-] or click
on the Calculator toolbar to insert a minus sign.
Inserting Parentheses
Mathcad places parentheses automatically to maintain the order of operations. You may want to place parentheses to clarify an expression or to change the overall structure of the expression. You can either insert a pair of parentheses all at once or insert one parenthesis at a time. We recommend you insert a pair since this avoids the possibility of unmatched parentheses.
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To enclose an expression with a pair of parentheses:
1.Click on the expression and press [Space] one or more times to place it between the editing lines.
2. Type the single-quote key [‘], or click |
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on the Calculator |
toolbar. The expression is now enclosed |
by |
parentheses. |
It is sometimes necessary to insert parentheses one at a time using the [(] and [)] keys. For example, to change a – b + c to a – (b + c):
1.Click just to the left of the b. Make sure the blue insertion line is on the left as shown. Press [Insert] if necessary to move it over.
2.Type [(] and click to the right of the c. Make sure the blue insertion line is to the right as shown. Press [Insert] if necessary to move it over.
3. Type [)].
Deleting Parentheses
Whenever you delete one parenthesis, Mathcad deletes the matched parenthesis. This prevents you from inadvertently creating an expression having unmatched parentheses.
To delete a matched pair of parentheses:
1. Move the editing lines to one side of the “(”.
2. Press [Backspace] or [Delete].
Moving Parts of an Expression
The menu commands Cut, Copy, and Paste from the Edit menu are useful for editing complicated expressions. Copy and Paste can be used to move parts or all of an expression from one place to another.
Suppose you want to build the expression:
cos(wt + x) + sin(wt + x)
1.Drag-select the argument to the cosine function.
2.Select Copy from the Edit menu, or right-click on the highlighted argument and select Copy.
3. Click on the placeholder for the sin function.
4.Select Paste from the Edit menu, or right-click on the placeholder and select Paste.