Mixed Grouping in Subequations

Question

I am looking to create a subequation environment with three equations. However, I want to group the 2nd and 3rd equations with a brace on the left side. I tried this (using the empheq package):

\begin{subequations}
 \begin{align}
   A&=B \\
 \end{align}
 \begin{empheq}[left=\empheqlbrace]{align}
   C&=D \\
   E&=F
 \end{empheq}
\end{subequations}

But the alignment (as expected) between the two sets of equations doesn't come out well. Any hints?

I'm sure the following should be of help: Aligning across aligned equation blocks; give some feedback on your findings. — Werner, Jun 25 '12 at 16:21
@Werner Thanks! That tip works great. Everything lines up automatically now (I had resigned myself to a bit of whitespace voodoo to get it done the other day). — Brian, Jun 26 '12 at 18:02

score 5 · Accepted Answer · edited Mar 20 '17 at 22:47

If you are willing to do some manual shifting:

\documentclass[a5paper]{article}
\usepackage{amsmath}
\newcommand{\leftstuff}[2][0pt]{\smash{\raisebox{#1}{\llap{#2}}}}

\begin{document}

\begin{subequations}
 \begin{align}
   A&=B \\
\leftstuff[-0.65em]{\Bigg\{\;}
   C&=D \\
   E&=F
 \end{align}
\end{subequations}

\end{document}

enter image description here

With the optional argument you shift the brace up or down, and I've manually specified the brace size (\Bigg) and the spacing (\;).

Mixed Grouping in Subequations

1 Answers1