I have an equation contained inside `\[...\]`

, which automatically makes a `\sum`

with sub- and superscripts turn big–so that the summation sign looks awkward inside parenthesis. Any idea how to make the parenthesis completely enclose the whole summation?

```
\documentclass{article}
\begin{document}
We have:
\[ \sum_{i=1}^n i = (\sum_{i=1}^{n-1} i) + n =
\frac{(n-1)(n)}{2} + n = \frac{n(n+1)}{2} \]
\end{document}
```

## Best Answer

The usual thing to do is replace

`(`

with`\left(`

and`)`

with`\right)`

, which automatically expand to fit the material between them. Note that every`\left...`

requires a`\right...`

(but the type of bracket may be different, i.e.`\left(...\right]`

also works).I would typeset your equation as

For manual control of sizes (most of the time you

won'tneed these)produce