Eqn numbers in aligned environment

Question

I want to write an equation with multiple cases, but that needs multiple aligned columns within each case. I also want a left brace (of my choosing) on the left. Something like this works:

\begin{equation}
F = 
\left\{ \begin{aligned} 
1.
& 2.
& \ &\text{First row} \\
3. 
& 4.
& \ &\text{Second row}
\end{aligned} \right.
\end{equation}

However, only one number is assigned to the group (simply the equation environment). I'd like to tag each individual row (of the aligned environment). is there a way to do this?

Also, you should be clear: do you want separate equation numbers or subequation numbers? i.e. 1,2 or 1.a,1.b? — Seamus, Jul 14 '11 at 16:33
@Seamus: I'm not sure how the link helps---in this case, I need an aligned environment within another. Re: separate or subequation, the ability to do both would be useful (not in the same block of equations), but not essential. — TSGM, Jul 14 '11 at 18:39

score 2 · Accepted Answer · edited Jul 15 '17 at 14:37

You can load the empheq package and then write

\begin{empheq}[left={F=\empheqlbrace}]{alignat=2}
a&=b &&\quad\text{first} \\
c&=d &&\quad\text{second} \\
e&=f &&\quad\text{third}
\end{empheq}

It doesn't mix well with left equation numbers, though. But in any case right equation numbers are preferable.

In this particular case align is not well suited, because it gives too much spacing between columns.

Eqn numbers in aligned environment

1 Answers1