# bigger parentheses in equations

I have the following TeX equation:

r = (I_n - (.85) M^T)^{-1} (\frac{1 - (.85)}{5}) \cdot 1 \\


I want bigger parentheses around the term (1-(.85)/5), how can I achieve this?

1. How can I get large parentheses?
2. Is there a general symbol for larger symbols such as \dfrac{}{} for fractions?
3. How can I do large brackets instead of parentheses?
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use \left(<content>\right) –  azetina Oct 23 '12 at 2:05
Regarding your third question: to get square brackets instead of round parentheses, just use [...] instead of (...). –  Mico Oct 23 '12 at 4:59

## 1 Answer

You can use the \left...\right construct for stretchable delimiters or some of the commands from the \bigl, \bigr family for bigger delimiters:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$r = (I_n - (.85)M^T)^{-1}\biggl(\frac{1 - (.85)}{5}\biggr)\cdot 1$

$r = (I_n - (.85)M^T)^{-1}\left(\frac{1 - (.85)}{5}\right)\cdot 1$

$r = (I_n - (.85)M^T)^{-1}\biggl[\frac{1 - (.85)}{5}\biggr]\cdot 1$

$r = (I_n - (.85)M^T)^{-1}\left[\frac{1 - (.85)}{5}\right]\cdot 1$

\end{document}


When to use one or the other depends; the \left...\right pairs must be balanced in every line of a multi-line displayed expression so you sometimes will have to use \left. and \right. (notice the final dot) to get proper balancing; and ven after balancing you might need to use a phantom to get an homogeneous height for the delimiters in separate lines. The "big" family of command don't suffer from these limitations.

Another case in which the "big" family produces better results is illustrated in the following simple example:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

Wrong result
$\lvert \lvert x \rvert - \lvert x \rvert \rvert \leq \lvert x-y \rvert.$

Wrong result
$\left\lvert \lvert x \rvert - \lvert x \rvert \right\rvert \leq \lvert x-y \rvert.$

Correct result
$\bigl\lvert \lvert x \rvert - \lvert x \rvert \bigr\rvert \leq \lvert x-y \rvert.$

\end{document}


A little example showing the sizes for the different commands of the "big" family in the case of an opening parenthesis:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{tabular}{@{}*{5}{c}@{}}
& \verb!\bigl! & \verb!\Bigl! & \verb!\biggl! & \verb!\Biggl! \\[1ex]
$($ & $\bigl($ & $\Bigl($ & $\biggl($ & $\Biggl($
\end{tabular}

\end{document}


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Can you add a link to where all the different sizes are described. I often get confused and use trial and error until I get the right size. I have thought of setting up a macro that accepts a number and does the translation to the appropriate big macro, but someone else must have done that already. –  Peter Grill Oct 23 '12 at 4:37
@PeterGrill I added a little example showing the sizes in one case. Is something like that what you had in mind? –  Gonzalo Medina Oct 23 '12 at 17:38
Thanks. I assume that that are all the available sizes. For some reason I thought there were more, –  Peter Grill Oct 23 '12 at 20:07