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# Subequations

The subequations environment provides a convenient way to number equations in a
group with a subordinate numbering scheme. For example, supposing that the current
equation number is 2.8, write

$$\label{first} a=b+c$$
some intervening text
\begin{subequations}\label{grp}
\begin{align}
a&=b+c\label{second}\\
d&=e+f+g\label{third}\\
h&=i+j\label{fourth}
\end{align}
\end{subequations}


to get

 LaTeX Markup problem Show/Hide latex markup \documentclass{article} \usepackage{amsmath} \usepackage{amsthm} \usepackage{amssymb} \usepackage{bm} \newcommand{\mx}[1]{\mathbf{\bm{#1}}} % Matrix command \newcommand{\vc}[1]{\mathbf{\bm{#1}}} % Vector command \newcommand{\T}{\text{T}} % Transpose \pagestyle{empty} \begin{document} $$\label{first}a=b+c$$some intervening text \begin{subequations}\label{grp}\begin{align} a&=b+c\label{second}\\ d&=e+f+g\label{third}\\ h&=i+j\label{fourth}\end{align}\end{subequations} \end{document}  Show/Hide latex error Unable to find DVI conversion log file.

By putting a \label command immediately after \begin{subequations } you can get a
reference to the parent number; \eqref{grp} from the above example would produce (2)
while \eqref {second } would produce (2a).

You can also use the subequations environment to skip an equation number but record it
in a label. This could be used to give an equation number to a Figure or list, for
example

$$ax = y\,,$$
with properties
\begin{subequations}
\label{list1}
\end{subequations}
\begin{itemize}
\item[(\ref{list1}.1)] $x$ and $y$ are vectors
\item[(\ref{list1}.2)] $a$ is a scalar
\end{itemize}
$$bx=cy\,.$$


gives

 LaTeX Markup problem Show/Hide latex markup \documentclass{article} \usepackage{amsmath} \usepackage{amsthm} \usepackage{amssymb} \usepackage{bm} \newcommand{\mx}[1]{\mathbf{\bm{#1}}} % Matrix command \newcommand{\vc}[1]{\mathbf{\bm{#1}}} % Vector command \newcommand{\T}{\text{T}} % Transpose \pagestyle{empty} \begin{document} $$ax = y\,,$$ with properties \begin{subequations} \label{list1} \end{subequations} \begin{itemize} \item[(2.1)] $x$ and $y$ are vectors \item[(2.2)] $a$ is a scalar \end{itemize} $$bx=cy\,.$$ \end{document}  Show/Hide latex error Unable to find DVI conversion log file.