2

Sometimes one needs to break a line that started with \left( to another line that ends with \right). This procedure can not be processed though using the command:

\begin{equation}
\begin{aligned}
....
\end{aligned}
\end{equation}

What to do in this case?

2
  • Welcome to TeX.SX! You can use backticks for in-line code highlighting and the {} symbol in the gui to highlight blocks of code. It is easier to help you if you add a minimal working example that takes the form \documentclass{...}\usepackage{....}\begin{document}...\end{document}. In this case it would help to highlght what problem you are having...it sounds to me as if you are misusing \left and \right.
    – user30471
    Aug 13, 2015 at 10:10
  • 4
    My experience says that you most likely don't need \left and \right. The real formula you want to typeset is needed in order to help; otherwise only conjectures can be made.
    – egreg
    Aug 13, 2015 at 10:19

4 Answers 4

3

Use \right. on the first line and \left. on the second, for example

\begin{equation}
\begin{aligned}
2x+y =& \left( \int_0^x dt+ \right. \\
    & \left. y+x\vphantom{\int_0^x dt} \right)
\end{aligned}
\end{equation}

Note that, if there is something very large on the first line, and not on the second, that the size of the brackets may not be the same. You can use \vphantom{...} to include the larger bit on the second line, but keeping it invisible, so your bracket sizes match.

5
  • Aha.. nice. What do '\right.' and '\left.' usually mean so I don't use them blindly? Another thing where to place '\vphantom{..}'? Aug 13, 2015 at 10:24
  • The commands \left. and \right. simply balance the opening and closing of the brackets, so LaTeX knows where to check the size of things to choose the correct bracket size. For the \vphantom, you can put it anywhere in between the \left and \right that need a different size. Aug 13, 2015 at 10:26
  • 3
    Sorry, but this is an example of useless \left and \right; you can also notice that the spacing between + and x in the second line is wrong.
    – egreg
    Aug 13, 2015 at 10:32
  • This worked for me just fine, thank you for your notice though @egreg. Aug 13, 2015 at 10:44
  • @egreg I agree the \left and \right were not needed at that point, it was simply an easy example of how the code could look. I'm not sure how to fix the spacing around the + easily though. Aug 13, 2015 at 11:54
3

Without seeing what problem you are having we have to guess, but the \left and \right's need to be balanced either side of the & alignment characters:

The following works fine:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
  \begin{equation}
  \begin{aligned}
  ....\left( x\right.&=\left.43\right)\\
  ....\left( x\right.&=\left.43\right)\\
  \end{aligned}
  \end{equation}
\end{document}
3

In the mathtoolsdocumentation, you a trick that allows for line breaks within delimiters, using the \DeclarePairedDelimiters command and a trick by Sébastien Gouezei (3.6.1 of the doc).

Demo:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage{lmodern}

\newcommand\MTkillspecial[1]{% helper macro
\bgroup
\catcode`\&=9
\let\\\relax%
\scantokens{#1}%
\egroup
}
\DeclarePairedDelimiter\brparen
\lparen\rparen
\reDeclarePairedDelimiterInnerWrapper\brparen{star}{
\mathopen{#1\vphantom{\MTkillspecial{#2}}\kern-\nulldelimiterspace\right.}
#2
\mathclose{\left.\kern-\nulldelimiterspace\vphantom{\MTkillspecial{#2}}#3}}

\begin{document}

\begin{equation}
A =\! \begin{aligned}[t]
 & \left(\sqrt{\frac{a}{B}} + b + c + d + e{}\right. \\
         & \left. + f +g + h\right)\
\end{aligned}
\end{equation}

\begin{equation}
A =\! \begin{aligned}[t]
  \brparen[\Bigg]{& \sqrt{\frac{a}{B}} + b + c + d + e{} \\
         & + f +g + h}\
\end{aligned}
\end{equation}

\begin{equation}
A =\! \begin{aligned}[t]
  \brparen*{& \frac{K^2}{L^2} + B + + C + D + E\\
         & + F + G + H}
\end{aligned}
\end{equation}
\end{document} 

enter image description here

2

You can terminate a line that starts with \left( by means of \right.. In the following line you will then probably have to type \left. to match the closing parenthesis \right)

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