Square roots, accents, and delimiters

To type a square root, just click on the button with a square root sign on it. The square root appears, and the cursor is in a new insertion point inside the square root. You can type variables, numbers, other square roots, fractions, whatever you want. LYX will automatically resize the square root to fit what's inside.

Accenting a character ( $\overrightarrow{v}$) or group of characters ( $\overrightarrow{a+b}$) is done the same way. The Decoration types are available from the panel. Click on a decoration, and LYX will insert that decoration with an insertion point under (or over) it. Just type what you want in the insertion point. There are two sets of decorations: those that resize with the text you type, and those that have fixed size, and are most appropriate for a single letter.

Delimiters such as parentheses, brackets, and braces work similarly, but are a bit more complicated. Hit the Delimiter button, which features a blue square surrounded by brackets, to pop up the Delimiter dialog. Your current selection of delimiters is displayed in a box. It's a pair of parentheses by default, but you can choose a pair of braces, a brace and a parenthesis, or even choose the empty square to have something like `` a = $\left\langle\vphantom{ 7}\right.$7'' (the empty delimiter is displayed as a broken line in LYX, but won't show up in the output).

If you're lazy, you can type actual parentheses in math mode, rather than using the Delimiter window. However, those parentheses will be the same size as regular text, which will look bad if you have a big fraction or matrix inside the parentheses. Using the Delimiter window will guarantee that the delimiters are sized based on what's inside them.

You can also put delimiters or a square root sign or a decoration on already existing text. Select the portion of the formula that you want to adjust, and then click on the button you want from the Math Panel. Try using this to change Newton's second law from scalar to vector form (f = ma to $\overrightarrow{f}$ = m$\overrightarrow{a}$). Once you've learned about matrices, this is how you'll put parentheses or brackets around them.