# How center align two equations separated by a line

I wanted to center align two logical equations that do not use "=" sign. I also want to separate the equations with a line. Currently I use aligned environment and midrule. Can the equations be center aligned instead of right aligned? The minimum working example is given below:

\documentclass[border=3mm,preview]{standalone}
\usepackage{amsmath}
\usepackage{booktabs}

\begin{document}

\begin{equation*}
\begin{aligned}
\forall_{t \in firing} \quad \forall_{a \in t \bullet} \quad a \in AN\\
\midrule
\mu^\prime_{an} = (\mu_{an} - \bullet t) \cup a, \quad c(a) = 0 \\
\end{aligned}
\end{equation*}
\end{document}


• What shall be aligned here actually? Wouldn't alignat* not better than a combination of equation* and aligned?
– user31729
Jan 26, 2017 at 16:01
• @ChristianHupfer - The OP may have used some unintentionally ambiguous terminology. Instead of "center aligned", it might be more felicitous to simply write "center".
– Mico
Jan 26, 2017 at 16:09

You could replace the aligned environment with a gathered environment, which centers its contents line by line.

\documentclass[border=3mm,preview]{standalone}
\usepackage{amsmath}
\usepackage{booktabs}
\begin{document}
\begin{equation*}
\begin{gathered} % 'gathered' instead of 'aligned'
\forall_{t \in \textit{firing}} \quad \forall_{a \in t \bullet} \quad a \in AN\\
\midrule
\mu^\prime_{an} = (\mu_{an} - \bullet t) \cup a, \quad c(a) = 0
\end{gathered}
\end{equation*}
\end{document}

• it works with gathered. Jan 27, 2017 at 4:58

I hope you understand your question. I add my MWE centering two logical equations without equal sign and separate the equations with a line.

\documentclass[a4paper]{article}
\usepackage{amsmath,amssymb,booktabs}
\begin{document}

$\begin{array}{@{}c@{}} \forall_{t\in\mathit{firing}} \quad \forall_{a\in t\bullet} \quad a\in AN \\ \specialrule{.05em}{1em}{0em}\\ \mu'_{an} = (\mu_{an} - \bullet t) \cup a, \quad c(a) = 0 \\[.5em] \specialrule{.2em}{.1em}{.1em} % optional \end{array}$

\end{document}


• Instead of using \multicolumn{4}{c}{$...$} for both rows, would it maybe be easier not to employ \begin{tabular}{llll} ... \end{tabular} and, instead, to employ $\begin{array}{c} ... \end{array}$?
– Mico
Jan 27, 2017 at 9:11
• You're right. When I entered the code I have not thought about it much. Compared much who is better than me. You can, if you like, change my code. Jan 27, 2017 at 16:38
• I've taken you up on the invitation to modify your code. Feel free to apply further changes.
– Mico
Jan 27, 2017 at 21:06
• @Mico Perfect. This way I learn new codes and shortcuts. Thanks a lot. Jan 28, 2017 at 8:29