# How to close \Big( with an invisible bracket?

When then opening and closing of a bracket are not on the same line, LaTeX demands 'invisible' brackets or it will get confused and not compile. Example:

\begin{equation}
\begin{aligned}
A = 5 & \left(  a + b + c + ...  \right. \\  % The '\right.' is invisible but needed to close the 'left)
& \left. d + e + f \right)
\end{aligned}
\end{equation}


I noticed that this behaviour doesn't work when instead of using \left( you use \Big (or any similar bracket size expression). The following doesn't compile:

\begin{equation}
\begin{aligned}
A = 5 & \Big(  a + b + c + ...  \right.
& \left. d + e + f \Big)
\end{aligned}
\end{equation}


It gives the following error:

 ? Missing } inserted.
<inserted text>
}
l.20    A = 5 & \Big( a + b + c + ...  \right
. \\
?


What does this mean and how can I solve it?

• with \Big( (or better \Bigl( you do not need to close it: it is a self standing bracket – David Carlisle Dec 7 '14 at 20:34
• Ah thanks, that actually makes sense of course, as it's more a character of fixed size, rather than an intelligent variable object like \left(. – Jelle Dec 7 '14 at 20:44
• @DavidCarlisle An answer? – egreg Mar 7 '15 at 21:04

With \Big( (or better \Bigl( you do not need to close it: it is a self standing bracket.
\left \right are different in that they need to see the intervening expression as a single math list in order to determine the size to stretch, which is why they can not span different cells in an align.