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I've just got a, what is, hopefully simple question about the use of the \begin{align} and \end{align} environment delimiters. I have a single equation to write in between such commands. 

\begin{align}
  \begin{split}
    A &= \left(B + \dots \\&+ \dots C \right)
  \end{split}
\end{align}

On one line I start the equation with a bracket which is fitted to the equation so make use of \left but the closure of this, defined by the corresponding \right bracket is on a different line and I am getting an error.

Is there an easy fix of this? Thanks!

Au101
  • 10,278
CAF
  • 1,003

1 Answers1

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\left( ... \right) cannot span lines.

Either use \right. and \left. like so:

\begin{align}
  \begin{split}
    A &= \left(B + \dots\right. \\
      &+ \left.\dots C \right)
  \end{split}
\end{align}

enter image description here

These basically insert an invisible closing/opening (respectively) delimeter, so that you always have a pair. A \left must be paired with a \right, but obviously you don't always want an actual delimeter printed, so we have \right. and \left..

Or you can use manually sized brackets, e.g. \bigl( ... \bigr)

Or you can just use normal brackets. Certainly, \left( ... \right) is not necessary here and overusing these can cause you problems, see:

"(" or "\left(" parentheses?

Is it ever bad to use \left and \right?

Community
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Au101
  • 10,278
  • Many thanks! It worked for me. And A,B.C were just generic letterings I used to represent the quantities actually appearing in my equation. – CAF Jan 14 '16 at 20:18
  • 1
    @CAF Ah, in that case, fair enough. But it is common for people (with the best of intentions) to overuse \left( ... \right), thinking it's giving them optimal scaling every time and we have a number of questions on this site where people would like them to be used by default. But, in fact, they should be used only where necessary and sometimes it's better to use manual sizing, like I say, if you do need a bigger delimeter – Au101 Jan 14 '16 at 20:20
  • Ok thanks for the comments and the quick reply! +1, accepted – CAF Jan 14 '16 at 20:27
  • actually, equation would be better here than align. since there's only one point of alignment, split takes care of that`, and there's only a single numbered expression, which is equivalent to a one-liner. – barbara beeton Jan 14 '16 at 21:14