Math & Science ⇒ Numbered lines in "cases"

[Adampe]

Hello,

I want to have numbered every line in \begin{cases} so I can later refer to it. I have tried sth like this:

Code: Select all

\begin{equation}
A = \begin{cases}
    B \\
    C
\end{cases}
\end{equation}

and this

Code: Select all

\begin{equation}
A = \left\{
\begin{array}{l}
    B \\
    C
\end{array}\right.
\end{equation}

but I have only one number:


How can I write this to have numbered every line?

[elingeniero]

You can use the cases package, an example of of its usage is given here:

Code: Select all

\documentclass{standalone}
\usepackage{amsmath}
\usepackage{cases}
\begin{document}
\begin{numcases}{f(x)=}
1&$x\geq0$\label{positive}\\
0&$x<0$\label{negative}
\end{numcases}

See the second case \ref{negative} or the first \ref{positive}

\begin{subnumcases}{f(x)=}
1&$x\geq0$\label{positive-subnum}\\
0&$x<0$\label{negative-subnum}
\end{subnumcases}

See the second case \ref{negative-subnum} or the first \ref{positive-subnum}
\end{document}

[Adampe]

Thank You very much, it is exactly what I need.