# Equation numbering inside aligned placed next to an alignedat

I have a group of equations on the left hand side and a group of explanations on the right hand side. Since the number of lines in both group differ from each other I use the aligned and alignedat for automatic alignment.

How do I get equation numbers for f_1 and f_2? There are a lot of similar questions like this on stackexchange, but the answers boil down to use another environment like align or split. This is not feasible in my case, since I would lose the automatic alignment.

Example:

\documentclass{scrartcl}
\usepackage{amsmath}

\begin{document}
\begin{aligned}[c] f_1 &= a + b\\ %1.1 here f_2 &= a - b\\ %1.2 here \end{aligned} \qquad \begin{alignedat}{2} a &= &&\text{ Some one line text}\\ b &= &&\text{ Some two line text}\\ &&&\text{ 2nd line}\\ \end{alignedat}
\end{document}


Additionally it would be nice if I could freely decide if the numbers would be place left, middle (like in the picture) or right of the equation.

Thanks for your time!

• Welcome to TeX.SE. Valid placement specifier options for an aligned environment are [t] ("top"), [c] (centered -- the default), and [b] ("bottom"). [r] is not a valid option and is simply ignored. – Mico Apr 15 '18 at 14:08

I don't think this is the best way to set the display.

\documentclass{scrartcl}
\usepackage{amsmath,varwidth}
\usepackage[nopar]{lipsum}

\begin{document}

\lipsum[3]
\begin{center}
\begin{minipage}{0.2\textwidth}% <--- adjust to the needed width
\vspace*{-\baselineskip}
\begin{flalign}
f_1 &= a + b &\\
f_2 &= a - b &
\end{flalign}
\end{minipage}
\begin{aligned} a &= \text{Some one line text}\\ b &= \begin{varwidth}[t]{0.7\textwidth} Some two line text\\ second line \end{varwidth} \end{aligned}
\end{center}
\lipsum[4]

\end{document}


Something like this?

\documentclass{scrartcl}
\usepackage{amsmath}
\numberwithin{equation}{section}
\begin{document}
\setcounter{section}{1} % just for this example

\noindent
\begin{minipage}{0.25\textwidth} % choose a suitable width
\setlength\abovedisplayskip{0pt}
\setlength\belowdisplayskip{0pt}
\begin{align}
f_1 &= a + b\\ %1.1 here
f_2 &= a - b   %1.2 here
\end{align}
\end{minipage}
\hspace{2cm} % or whatever spacing amount is desired
\begin{minipage}{0.6\textwidth}
\begin{aligned} a &= \text{A first line of text}\\ b &= \text{A second line of text}\\ &\quad \text{ And a third line} \end{aligned}
\end{minipage}
\end{document}

• Thanks for the minipage idea! But I'll go with egreg, because the without the second minipage, I get automatic horizontal alignment between the equations and the text. – user3608078 Apr 17 '18 at 18:23