big angle brackets

Question

I know that \langle and \rangle creates left and right angle brackets. But they don't seem to adopt to the size of the expression inside. For example, if I have a big matrix, I would like to angle brackets to be big as well. How can I get this effect?

Answer 1

The mtpro2 package (MathTime Professional II) provides extra-large (up to 10 cm tall) fence symbols -- round parentheses, square brackets, curly braces, angle brackets, etc. -- via its \LEFTRIGHT command. Note that the full mtpro2 package isn't free of charge; however, its "lite" subset, which is all that's needed to produce extra-large fence symbols, is free of charge.

\documentclass{article}
\usepackage[lite]{mtpro2}
\begin{document}
\[
\LEFTRIGHT\langle\rangle{
\begin{array}{c} 
  1\\2\\3\\4\\5\\6\\7\\8\\9\\10
\end{array}}
\]
\end{document}

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update 2020-10-01: The pctex.com site noted in my answer no longer seems provide a functioning link to the page from which the lite subset of the mtpro2 package used to be available for downloading. Many thanks to @mateuszb for bringing this issue to my attention.

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Answer 2

In the standard fonts \langle has a fixed upper limit and doesn't grow above a certain size. (TeX extends characters by adding vertical extension glyphs and angle brackets don't have a vertical section that can be extended). However if you don't mind distorting the shape you can scale the bracket to fit:

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\begin{document}

\[
\left\langle\begin{array}{c}1\\2\\3\\4\\5\\6\end{array}\right\rangle
\]

\[
\sbox0{$\begin{array}{c}1\\2\\3\\4\\5\\6\end{array}$}
\mathopen{\resizebox{1.2\width}{\ht0}{$\Bigg\langle$}}
\usebox{0}
\mathclose{\resizebox{1.2\width}{\ht0}{$\Bigg\rangle$}}
\]

\end{document}

Answer 3

This is the sort of thing the scalerel package was designed for. WIth the use of the width-limited \scaleleftright or aspect-limited \stretchleftright, a desirable outcome can often be achieved. In the below example, I show both, first employing \scaleleftright with a width limit of 1.75ex, and then showing \stretchleftright with an aspect limit of 1000% (i.e. stretch of 10). Note that in all cases, the symbols being manipulated are the humble < and > symbols, not some predefined stretchable version.

Finally, in the third figure set, I show that one can use a stretched version of \langle and \rangle, instead of < and >. Depending on the tastes of the user, one may be preferable to the other.

\documentclass{article}
\usepackage{scalerel}
\begin{document}
\setlength\arraycolsep{0ex}
(
\scaleleftright{<}
{x}
{>}
%
\scaleleftright[1.75ex]{<}
{\begin{array}{c}x\y\z \end{array}}
{>}
%
\scaleleftright[1.75ex]{<}
{\begin{array}{c}u\v\w\x\y\z \end{array}}
{>}
%
\scaleleftright[1.75ex]{<}
{\begin{array}{c}r\s\t\u\v\w\x\y\z \end{array}}
{>}
)
(
\stretchleftright{<}
{x}
{>}
%
\stretchleftright[1000]{<}
{\begin{array}{c}x\y\z \end{array}}
{>}
%
\stretchleftright[1000]{<}
{\begin{array}{c}u\v\w\x\y\z \end{array}}
{>}
%
\stretchleftright[1000]{<}
{\begin{array}{c}r\s\t\u\v\w\x\y\z \end{array}}
{>}
)
(
\stretchleftright{\langle}
{x}
{\rangle}
%
\stretchleftright[1000]{\langle}
{\begin{array}{c}x\y\z \end{array}}
{\rangle}
%
\stretchleftright[1000]{\langle}
{\begin{array}{c}u\v\w\x\y\z \end{array}}
{\rangle}
%
\stretchleftright[1000]{\langle}
{\begin{array}{c}r\s\t\u\v\w\x\y\z \end{array}}
{\rangle}
)
\end{document}

Answer 4

The nicest solution I can think of is using the braket package.

\documentclass[class=article,border=5pt]{standalone}
\usepackage{braket}
\begin{document}
$
\Braket{
    \begin{array}{lcl}
               z & =  a \
                 & =  a \
        f(x,y,z) & =  x + y + z
    \end{array}
}
$
$
\Braket{
    \begin{array}{lcl}
               z & =  \frac{a}{b} \[2ex]
                 & =  \frac{a}{b} \[2ex]
        f(x,y,z) & =  x + y + z
    \end{array}
}
$
\end{document}

to get right angle brackets which adjust to size. Unfortunately, like other solutions here the brackets do not stretch when the vertical line spacing is increased.