[Tex/LaTex] System of equation, left aligned and two lines numbered

alignempheqhorizontal alignmentlabels

I really don't find how to create the system I am looking for, so I am asking for a little help!
I want :

  1. At least two columns aligned to the left;
  2. The system name and a big brace on the left;
  3. Some lines with a label (but not each lines).

Currently the best I found is to use empheq and align. Here is an example:

\documentclass[15pt , a4paper]{article}
\usepackage{empheq}

\begin{document}

\begin{empheq}[left=(P)\empheqlbrace]{align}
  bigvariable =b& big info\notag\\ 
  c =d& info2\label{eq:1}\\
  e =f& info3\label{eq:2}
\end{empheq}

\ref{eq:1} \ref{eq:2}

\end{document}

However, with align, the first column is aligned to the right and the second to the left (and not both to the left). I could add "&" before each line but in that case the second column is aligned to the right.

I tried to use an array but I only succeed in setting one label (via : \addtocounter{equation}{1}\tag{\theequation}\label{eq:1}). The following labels are ignored.

Do you have any idea?

Best Answer

How about

\begin{empheq}[left=(P)\empheqlbrace]{alignat=2}
  bigvariable &=b &\qquad&\text{big info}\notag\\ 
  c &=d &&\text{info2}\label{eq:1}\\
  e &=f &&\text{info3}\label{eq:2}
\end{empheq}

Use alignat to give columns with adjustable spaces inbetween.

enter image description here

Related Question