Re: \underbrace spanning multiple lines



pechyony@xxxxxxxxxxxxxxxxx wrote:
Is there any way to underbrace mathematical expression taking several
lines. I'd like to do something like
\begin{equation}
\begin{split}
A = & \underbrace{ B + \\
    & C +}_{xxx} \\
    & D
\end{split}
\end{equation}
but it does not pass Latex compilation.

Thanks in advance,
Dmitry Pechyony


the above does of course not work because of the line breaks.

Here is a proof of concept showing that it could be done

\documentclass{article}
\usepackage{mathtools} % auto loads amsmath
\begin{document}
\begin{equation}
  \begin{split}
    a &= b +c +g +r_q \\
    &\quad \underbrace{
      \mathmakebox[\widthof{$\displaystyle b +c +g +r_q$}][l]{
        + x+y}}_{xxx}
  \end{split}
\end{equation}
\end{document}

It not optimized at all, just showing that it can be done

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