To delete an operator connecting two variable names or constants:

• Place the editing lines after the operator.

• Press the [BkSp] key.

Now you can easily insert a new operator to replace the one you deleted just by typing it in.You can also delete an operator by placing the editing lines before it and pressing the[Delete] key instead. For example:

• Place the editing lines before the operator..4

• Press the [Delete] key.In the above examples, it is easy to see what “before” and “after” mean because theexpressions involved naturally flow from left to right, the same way we read. Fractionsbehave the same way. Since we would naturally say “a over b,” putting the editing lines”after” the division bar means putting them just before the b. Similarly, putting theediting lines “before” the division bar means putting them immediately after the a. Thefollowing example illustrates this:For certain operators, it may not be clear where to put the editing lines. For example,it is not clear when looking at Ixl or x what “before” and “after” mean. When thishappens, Mathcad resolves the ambiguity by referring to the spoken form of theexpression. For example, since you would read x as “x conjugate,” the bar is treatedas being after the x.

• Here, the two editing lines hold only the 1[8] numerator. This means any operator youtype will apply only to the numerator.

• Typing *c results in this expression. Note how the expression held betweenthe editing lines became the first operandof the multiplication.

• Here, the editing lines hold the entire1[8] fraction. This means any operator youtype will apply to the entire fraction.

• Typing *c results in this expression. 1[8] Note how the everything between theediting lines became the first operand ofthe multiplication.

• Here, the editing lines hold the entire fraction as they did in the previous exam- IBple. However, this time the vertical editingline is on the left side instead of onthe right side.Typing *c results in this expression.Note how the expression enclosed by theecliting lines became the second ratherthan the first operand of the multiplication.

This happened because the verticalediting line was on the left side rather than the right side.Now that you know the significance of what’s held between these two editing lines, thepertinent question becomes “How do I control what’s held between the two editing

lines?”One way to control the length of the editing lines is to click on an operator. When youclick on an operator, you make the pair of editing lines hold that operator together witheverything that operator applies to. Depending on exactly where on the operator youclick, you’ll find the vertical editing line either on the left or on the right. Use the[Insert] key to move it from one side completely to the other, or use the left andright arrow keys to move a character at a time.A second way to control the length of the two editing lines is to press [Space] to cyclethrough all possible positions of the editing lines. Each time you press [Space] theecliting lines grow progressively longer. As they do so, they enclose more and more ofthe expression, until eventually, they enclose the entire expression. Pressing [Space]one more time brings the editing lines back to where they were when you started.The following example walks you through a short cycle:This is the starting position. The twoediting lines hold just the single variable”d.”

• Pressing [Space] makes the editinglines grow so that they now hold theentire denominator.Pressing [Space] once makes the editinglines grow again so that they nowhold the entire expression.

• At this point, the editing lines can’t becomeany longer. Pressing [Space]brings the editing lines back to the startingpoint of the cycle.

You’ll notice that in stepping through the previous cycle there was never an intermediatestep in which the editing lines held just the numerator. Nor was there ever a step inwhich the editing lines held just the a or just the b in the numerator. That’s because thesequence of steps the editing lines go through as you press [Space] depends on thestarting point of the cycle.II This is the starting position. The twoediting lines hold just the single variable”d.”

• Pressing [Space] makes the editing lines grow so that they now hold theen tire denominator.

To set the starting point of the cycle, you can either click on the appropriate part of the expression as described earlier, or you can use the arrow keys to move around the expression. The arrow keys walk the editing lines through the expression in the indicated direction. Keep in mind however that the idea of “up” and “down” or “left”and “right” may not always be clear, particularly when the expression becomes very complicated or when the expression involves summations, integrals and other advanced operators