# Mix align and enumerate

Is it possible to mix align* and enumerate, for example I want to TeX something like this (item a) and d), b) and e) and c) and f) should be aligned)

a) x^2 + y^2 = 1 b) a + b = c c) r-x = y+z

d) f - y = z e) ... f) ...

For example:

\begin{enumerate}
\begin{align*}
&\item x^2 + y^2 = 1 & &\item a + b = c & &\item r-x = y+z \\
&\item f - y = z & & \item ... & &\item ...
\end{align*}
\end{enumerate}


doesn't work.

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Welcome to tex.sx! A suggestion: Change your username to something more telling than "user4011". –  lockstep Mar 6 '11 at 14:56
An equation-per-line solution is given by the subequations environment from amsmath. –  Andrey Vihrov Mar 6 '11 at 14:59
Related question: force aligned equation all the way to the left –  Peter Grill Sep 8 '11 at 18:09

## Aligning at the equation tags

align* is not required if you just wish to align the items. Here's an example using multienum:

\documentclass{article}
\usepackage{multienum}
\renewcommand{\regularlisti}{\setcounter{multienumi}{0}%
\renewcommand{\labelenumi}%
\begin{document}
\begin{multienumerate}
\mitemxxx{$$x^2 + y^2 = 1$$}{$$a + b = c$$}{$$r-x = y+z$$}
\mitemxxx{$$f - y = z$$}{$$a - b = 2d$$}{$$r+x = 2y-3z$$}
\end{multienumerate}
\end{document}


## Aligning relation symbols and equation tags

If you wish to align both at relation symbols and on equation numbers, I recommend to use the alignat* environment. Mark alignment points by &, further use & to separate columns. The argument to alignat* specifies the number of columns. Here we've got six columns: three for the tags and three for the equations.

\documentclass{article}
\usepackage{amsmath}
\newcounter{eqn}
\renewcommand*{\theeqn}{\alph{eqn})}
\begin{document}
\begin{alignat*}{6}
\num&& x^2 + y^2 &= 1 \qquad& \num&& a + b &= c
&  \num&& r-x &= y+z \\
\num&\quad& f - y &= z      & \num&& a - b &= 2d
\qquad&  \num&& r+x &= 2y-3z
\end{alignat*}
\end{document}


I used automatic numbering. You could do it manually as well, just take care of the font, the tags should be in text font. So they don't look like variables.

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Please could show the variant with alignat* too? (align both relation symbols and equation numbers)? –  student Mar 6 '11 at 15:56
@user4011: With pleasure, I added an alignat* version. –  Stefan Kottwitz Mar 6 '11 at 16:18
Thanks. However in your first example the distance between the numbering (a),b) etc) and the equations was better... Is possible to have additionally equal distances between numbering and equations for the alignat variant? (And how to control this distance) –  student Mar 6 '11 at 16:31
@user4011: Change the \quad in the definition of \num to anything you like, perhaps just to ~. I just used \quad to produce some space. Similarly, you can replace the \qquad by any horizontal spacing command, such as \hspace{...}. –  Stefan Kottwitz Mar 6 '11 at 16:37
Ok, thanks again! –  student Mar 6 '11 at 16:45

One option would be to use a tabular environment:

\documentclass[a4paper]{article}
\usepackage{array}

\newcounter{myc}
\newcommand*\mitem{\stepcounter{myc}\alph{myc})}

\begin{document}

{
\centering
\begin{tabular}{*{3}{>{\makebox[1em]{\hfill\mitem}\hspace{4pt}$}l<{$}}}
x^2 + y^2 = 1 & a + b = c & r-x = y+z \\
f - y = z &  a=b+c+f+g & t=s-r
\end{tabular}\par
}

\end{document}

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