You can get all different kinds of sizes of parentheses, brackets, curly brackets, etc. to make your formulas look good. Typing

$$ \Biggl( \biggl( \Bigl( \bigl( ( ) \bigr) \Bigr) \biggr) \Biggr) $$gives you

Analogous commands work for `[`

and `\{`

. Note
the used to get curly braces.

You can also let figure out how big a pair of
parentheses should be to fit the contained expression.
Use `\left(`

and `\right)`

, like this:

$$ \left(\sum a_i^2\right)^{1/2} $$gives

Of course, you can also use `\left[`

, `\right]`

,
`\left\{`

and `\right\}`

.