2.1 The basics  (Page 2/5)

The MathML editor will correctly parse a sequence of text and numbers and keyboard shortcuts into operators and arguments. For instance, 3-4 will be interpreted as "3 minus 4", and 3/(x+9) will be interpreted as "3 divided by the quantity x plus 9".

The second way to create operations using the keyboard is to type out the MathML name. This is analogous to choosing the operation from the toolbar menus and is discussed in the same section .

An example

With a blank MathML editor open , try typing in the following (or copying it from here and pasting into the editor):

Hit Enter . The MathML editor will display this as:

$x^2+bx$

Notice that we had to be explicit about our operations. Although most textbooks, and even our MathML editor, represents the product visually by printing $b()$ and $x()$ next to one another, we had to explicitly mark the multiplication. The editor will display the times operation in different ways, depending on the surrounding operations.

If you try to represent the product of $b()$ and $x()$ with bx , that portion of your expression will be highlighted, indicating that there is a problem with the code that must be fixed before being used in a module. Simply click on $bx$ and replace it with b*x .

Navigating through an expression

If you have just created an expression and pressed Enter , tight now your cursor should be at the right edge of your expression. If it isn't, click somewhere within your expression, and press the right arrow key until the cursor no longer moves and the path no longer changes in the Path bar. In this position, the Path bar should display Path: / plus and the entire expression should have a light grey background.

Press the left arrow key once. The cursor should still be on the right-hand side of the expression, but the Path bar should read: Path: / plus / times and now only the $bx$ term should have a light grey background.

Press the left arrow again. Now the $x()$ should appear within a block and be selected. The path will change again to Path: / plus / times / ci The term ci represents an "identifier", in this case our variable $x()$ .

Continue pressing the left arrow key across your expression to see what happens. Notice that once you reach the left side of the $b()$ , the path should again read Path: / plus / times and the product $bx$ should have a light grey background. When you reach the far left side of the expression, the path should again read Path: / plus and the entire expression should have a light grey background.

What is going on here?

MathML treats operators and their arguments as nested elements. In our example of $x^2+bx$ , $b()$ and $x()$ are both arguments of the operation called times . The product "b times x" is just one argument within the plus operation. The other argument of the plus operation is of course $x^2$ . This power operation itself has two arguments: $x()$ and 2. In this way, $b()$ is more closely bound to $x()$ than it is to either argument of the power operator.

We could picture these operators and arguments in a parenthetical structure: ( ( (x)^(2) ) + ( (b)*(x) ) ) The parentheses group arguments of each operator together. A set of parentheses encloses each number or variable separately, and a set of parentheses encloses each entire operation - for instance, the entire product $bx$ or the entire sum $x^2+bx$ .