Placing a tikzpicture next to an align and add an equation number

Question

I want to place a tikzpicture next to an equation and equip both of them together with an equation number. The reason is that the tikzpicture is a kind of explanation (visualization) for the equation. Therefore I prefer that both appear together as one "equation".

In Placing a tikzpicture next to an align it is explained how to place a tikzpicture next to an align environment using minipages. This works for me, but I have problems equipping the result with an equation number. I tried to enclose both minipages in an equation environment, but this does not really work.

• If I use align inside one of the minipages, I get two equation numbers (one for align, the other one for equation, but both actually being the name number). I would expect this, expect from both equation numbers being the same, but this is probably related to the fact that I place align inside equation. I guess one is not supposed to do this.

• If I use align* inside one of the minipages, I get no equation number at all, also the equation environment does not carry an equation number. I would expect an equation number for the equation environment.

The result of the following example looks as follows:

\documentclass[10pt]{article}

\usepackage{tikz}
\usetikzlibrary{matrix,arrows}
\usepackage{mathtools}

\usepackage[english]{babel}
\begin{document}

\begin{equation}
\begin{minipage}{0.40\linewidth}
    \begin{align*}
    A=B
    \end{align*}
\end{minipage}
\begin{minipage}{0.40\linewidth}
\begin{center}
\begin{tikzpicture}
    \matrix (m) [matrix of math nodes, column sep=20pt]
    {
        A & B \\
    };
    \path[->,font=\scriptsize,>=angle 90]
    (m-1-1) edge (m-1-2);
\end{tikzpicture}
\end{center}
\end{minipage}
\end{equation}

\begin{equation}
\begin{minipage}{0.40\linewidth}
    \begin{align}
    A=B
    \end{align}
\end{minipage}
\begin{minipage}{0.40\linewidth}
\begin{center}
\begin{tikzpicture}
    \matrix (m) [matrix of math nodes, column sep=20pt]
    {
        A & B \\
    };
    \path[->,font=\scriptsize,>=angle 90]
    (m-1-1) edge (m-1-2);
\end{tikzpicture}
\end{center}
\end{minipage}
\end{equation}
\end{document}

Answer 1

I don't quite understand the question but here are two options;

\documentclass[10pt]{article}
\usepackage{tikz,mathtools}
\usetikzlibrary{matrix,arrows}

\begin{document}
\begin{align}
  A&=B & \begin{tikzpicture}[baseline]
         \matrix (m) [circle,fill=yellow,matrix of math nodes, column sep=20pt,
                 ampersand replacement=\&]
              {
                  A \& B \\
                  C \& D \\
              };
              \draw[-angle 90,font=\scriptsize]  (m-1-1) -- (m-1-2);
          \end{tikzpicture} \\
  C&=D &
\end{align}

\begin{minipage}{0.4\textwidth}
\begin{align}
  A&=B \\
  C&=D 
\end{align}
\end{minipage}\hspace{2cm}
\begin{tikzpicture}[baseline]
\matrix (m) [circle,fill=yellow,matrix of math nodes, column sep=20pt,
        ampersand replacement=\&]
     {
         A \& B \\
         C \& D \\
     };
     \draw[-angle 90,font=\scriptsize]  (m-1-1) -- (m-1-2);
\end{tikzpicture}
\end{document}