# reference equation inside line with several equations

I would like to use a reference style that I've seen in some older papers where the author will have several equations in the same line, but only one reference number for all of them. Then if the author wants to reference just one of the equations in that line, they will use a subscript or superscript to do so. Example:

a+b=c ; a*b=d  .................. (1)


Therefore, the equation with a sum a+b=c is given by equation (1)a.

Here is a MWE:

\documentclass[12pt]{article}
\usepackage{amsmath} % Extra Math Stuff
\begin{document}

I would like to have 3 equations together like this
$$A+B=C %\label{eq:sum} \quad\textrm{,}\quad A\times B=D %\label{eq:mul} \qquad\textrm{,}\quad A/B=D %\label{eq:div} \label{eq:tog}$$

And now I would like to either reference all equations in \eqref{eq:tog} or each of them individually, which should look like \eqref{eq:tog}$_a$, \eqref{eq:tog}$_b$ and \eqref{eq:tog}$_c$.

\end{document}

• You mean that you would like a different way of doing this than is shown in your MWE? The solution you already have is by far the most natural and easiest way to do this. If you don't like this way of doing it then can you add some more detail saying what sort of solution you would like? – Andrew Nov 9 '16 at 1:27

\eqref sets the reference in \upshape using double nesting (from amsmath.dtx):

\newcommand{\eqref}[1]{\textup{\tagform@{\ref{#1}}}}


What I've done below is to create a manual reference that assumes you'll use \eqref{<subref>}, and therefore delays the printing of the sub-equation number by two groups (using a nested \AfterGroup from etextools):

\documentclass{article}

\usepackage{amsmath,etextools}

\newcounter{subeqn}[equation]
\renewcommand{\thesubeqn}{\alph{subeqn}}
\makeatletter
\newcommand{\sublabel}[1]{{%
\stepcounter{subeqn}
\def\@currentlabel{\theequation\protect\AfterGroup{\protect\AfterGroup{\protect\textsubscript{\thesubeqn}}}}%
\ltx@label{#1}%
}}
\makeatother

\begin{document}

I would like to have 3 equations together like this:
$$A + B = C \sublabel{eq:sum} \textrm{,}\qquad A \times B = D \sublabel{eq:mul} \textrm{,}\qquad A \div B = D \sublabel{eq:div} \label{eq:tog}$$

And now I would like to either reference all equations in \eqref{eq:tog}
or each of them individually, which should look like \eqref{eq:tog}$_a$,
\eqref{eq:tog}$_b$ and \eqref{eq:tog}$_c$.

And now I would like to either reference all equations in \eqref{eq:tog}
or each of them individually, which should look like \eqref{eq:sum},
\eqref{eq:mul} and \eqref{eq:div}.

\end{document}

• Note: You must use \eqref to reference the sub-equations. – Werner Nov 9 '16 at 17:45