[texhax] Simultaneous Equations?

[E. Krishnan]

On Thu, 12 Feb 2004, Gavin Baker wrote:

> I just want two numbered equations, with one { to the left of them.
> I'm using LaTeX.

Here's a somewhat crude methosd I used to get numbered "cases" in 
equations, which is similar to your requirements.

    

     \usepackage{amsmath}
     \usepackage{calc}		

	\newenvironment{ncases}[4]{%
  	  \parbox{\textwidth-2cm}{%
            \begin{equation*}
              #1=
             \begin{cases}
               #2
             \end{cases}
           \end{equation*}}
           \hfill
           \parbox{1cm}{%
             \begin{eqnarray}
               {}\label{#3}\\
               {}\label{#4}
             \end{eqnarray}}}


     \begin{document}

       \begin{ncases}
         {|x|}{x, &\text{if $x\ge 0$}\\
         -x,&\text{if $x\le 0$}}{pos}{neg}
       \end{ncase}

       From this it easily follows that 
       \begin{equation}
        |x|\ge0\;\text{for all $x\in R$}
      \end{equation}
      for if $x\ge 0$, then by Equation~\eqref{pos}, we have $|x|=x\ge0$ and 
      if $x\le0$, then by Equation~\eqref{neg}, we have $|x|=-x\ge0$. 


-- 
Krishnan