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I have a multi-line equation that I want to have matching sized parentheses. The advice I read online was to use \left( equation \right. \\ left. rest-of-equation \right) . However, this syntax leaves first half of the equation unaware of what is in the second half. For example, if you include a square root term after the break, the second parenthesis will be larger than the opening parenthesis. When you are using the aligned environment to split a long equation this can look somewhat offputting.

alt text

Compare the top equation to the bottom one. The parentheses match in size for the bottom equation, but the left hand parentheses for the top one is noticeably smaller.

Top Code:

 \begin{aligned}[t] 
 \gamma_{\text{u}} + \frac{1}{108} 
 \left(57\gamma_{\text{er}} \right. &+  38\gamma_{\text{se}}\\ & {}\pm
 \left.\sqrt{2601 \gamma_{\text{er}}^2 + 3648
 \gamma_{\text{er}}\gamma_{\text{se}} + 1444 \gamma_{\text{se}}^2}
 \right) 
 \end{aligned}

Bottom Code:

\begin{aligned}[t] \gamma_{\text{u}} + \frac{1}{16}
\left(9\gamma_{\text{er}}  +  6\gamma_{\text{se}} \pm  \sqrt{49
\gamma_{\text{er}}^2 + 76 \gamma_{\text{er}}\gamma_{\text{se}} + 36
\gamma_{\text{se}}^2} \right) \end{aligned}
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2 Answers 2

up vote 12 down vote accepted

You could also put all parts on all lines and hide the ones that don't belong with \vphantom{...}. That way, they'll contribute to the height, but not take up space, and your parens should match. (Me personally, I find that clutters the source too much and I'm not too fond of \left and \right anyway, so I do \bigg et al. manually in these situations.)

I also vaguely recall seeing a re-implementation that works across multiple lines, and that appears to be in breqn.

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That is definitely a solution (\vphantom), but this is a table of multiline equations with 4 other columns in the table, so the source is already cluttered as it is :D. –  crasic Nov 18 '10 at 21:19
5  
I'd manually size them then. I think the order is \big \Big \bigg \Bigg, but I keep forgetting. –  Ulrich Schwarz Nov 18 '10 at 21:23

This is quite an old discussion but in case somebody still has a problem like that I'd recommend looking it up here http://en.wikibooks.org/wiki/LaTeX/Advanced_Mathematics#align_and_align.2A. They suggest that you should use \right. and \left. when you go to the next line. Then sizes and everything will fit and you won't have your source code completely clattered up by \vphantom stuff.

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3  
if you read the cited wikibooks entry more carefully, you will notice that if the scope of the "fenced" material exceeds a single line vertically, the \vphantom is still required on a line that doesn't have the same "highs" and "lows" as the line that it's supposed to match. –  barbara beeton Feb 14 at 19:06

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