subequations and array in braces
(Update according to egreg's commend. Thanks!)
The first example of empheq given by Bernard is invalid if omitting the overload option when loading empheq package. For the latex file provided by Bernard, it has no problems at all. However, when I used \usepackage[overload]{empheq}
in IEEEtrans with a lot other packages loaded, it will freeze the pdflatex
on my computer, I cannot see why, so I loaded it without overload
option. Here is the version when loading empheq
without overload
option (\empheqlbrace
is the big left parenthesis. \,
is just used to add extra space; the default is too tight.):
\begin{subequations}
\begin{empheq}[left={K(A)=\empheqlbrace\,}]{align}
& (I \otimes e^A) \psi\left(A^T \oplus (-A) \right) \\
& (e^{A^T/2} \otimes e^{A/2}) \operatorname{sinch}\left(\frac{1}{2}[A^T \oplus (-A)]\right) \\
& \frac{1}{2}(e^{A^T} \oplus e^A) \tau\left(\frac{1}{2}[e^T \oplus (-A)]\right),
\end{empheq}
\end{subequations}
whose output looks like:
For a question on citations, it works out of box, e.g. see the following codes:
\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\usepackage{empheq}
\begin{document}
We refer to the subequation (\ref{eq:2}) and the whole equation (\ref{eq:all}).
\begin{subequations}
\label{eq:all}
\begin{empheq}[left={K(A)=\empheqlbrace\,}]{align}
& (I \otimes e^A) \psi\left(A^T \oplus (-A) \right)
\label{eq:1} \\
& (e^{A^T/2} \otimes e^{A/2}) \operatorname{sinch}\left(\frac{1}{2}[A^T
\oplus (-A)]\right)
\label{eq:2}\\
& \frac{1}{2}(e^{A^T} \oplus e^A) \tau\left(\frac{1}{2}[e^T \oplus
(-A)]\right),
\label{eq:3}
\end{empheq}
\end{subequations}
\end{document}
which gives
Two solutions: one with the empheq
package and an align
environment, another with the subnumcases
environment from the cases
package. I had to adjust spacing for the brace in both, as I found the default was not so good (too small in the first case, too large in the second):
\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[overload]{empheq}
\usepackage{cases}
\begin{document}
\begin{subequations}
\begin{align}[left = \empheqlbrace\,]
& a = b \\
& c = d
\end{align}
\end{subequations}
\begin{subnumcases}{}
\!\! a = b \\
\!\! c = d
\end{subnumcases}
\end{document}