6

I've been running into a strange issue. I'm doing some derivations in LaTeX document, and am using the align environment to do so. Some derivations require multi-line brackets, for which I try to use

\left( \right. \\
\left. \right)

However, when I want to align my equations with something inside these brackets, I run into errors. Example:

\begin{align}
blablabla x=y \left(5 + 3 & + \right. \\
& \left. + 1 + 9 + 7 \right)
\end{align}

This runs into trouble, while

\begin{align}
blablabla & \left(5 + 3 + \right. \\
& \left. + 1 + 9 + 7 \right)
\end{align}

works just fine. Hence, I strongly suspect that the problem is caused by the first ampersand being inside the \left( ... \right) environment. Is there any way to get this to work? Any help would be much appreciated.

EDIT: For clarity: I'm looking for a way around the ampersand problem: I would like to have the ampersand inside my \left( ... \right) environment. Is there any way to do this?

4

A simplified version of your code:

\begin{align}
x = y \left(5 + 3 & + 1\right. 
\end{align}

I strongly suspect that the problem is caused by the ampersand being inside the \left( ... \right. [construct]. ... Is there any way to get this to work?

Your suspicion is correct. A short answer to your question: "No." Medium-length answer: "No way." Long answer: "Hell No."

Why? A \left ... \right pair creates a so-called "math-inner" item. What's inside a math-inner item is, well, not "visible" to the outside world. In particular, the & character cannot be "seen" by the align environment. Since such code cannot be made to work, LaTeX is programmed to throw an error message and stop.

The following code will not throw an error message; however, the sizes of the parentheses may not be what you need:

x = y \left(5 + 3 \right. & \left. + 1\right)

The upshot? Don't overuse left and right! Fortunately, sizing large parentheses manually is not that difficult to accomplish.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.