# How can I draw a big equality in a commutative diagram with extensions?

Here is the figure I want to draw:

I know how to draw a commutative square, like this:

$\begin{tikzcd}[sep = large] 0 \ar[r] & A \ar[d]\ar[r] & B \ar[d]\ar[r] & C \ar[d]\ar[r] & 0 & (a) \\ 0 \ar[r] & X \ar[d]\ar[r] & Y \ar[d]\ar[r] & Z \ar[d]\ar[r] & 0 & (b)\\ \end{tikzcd}$


How can I add a big equality sign instead of an arrow and how can I start from the bottom by the sequence given in my picture?

• Via this post, does =\joinrel= or =\joinrel=\joinrel= (etc.) work for you? – 542goweast May 16 at 22:58

Already in TikZ there is a key double equal sign distance which allows you to draw double lines with the appropriate distance between the lines.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz-cd}
\begin{document}
$\begin{tikzcd}[sep = large] & & \Sigma M\ar[r,-,double equal sign distance,double] \arrow[d,"f"']& \Sigma M \arrow[d,"\text{pinch}"]& & \\ M\vee M \vee M \ar[r,"{(\lambda_1,\lambda_2,\lambda_3)}"]& N \arrow[r]& X \arrow[r]& \Sigma M\vee\Sigma M \vee\Sigma M\\ \end{tikzcd}$
\end{document}


With another alignment of the rightmost vertical arrow, thanks to mathtools:

\documentclass{article}
\usepackage{tikz-cd, mathtools}

\begin{document}

\begin{tikzcd}[column sep=large, row sep=huge]
& & \Sigma M \dar["f", swap]\rar[equal]& \Sigma M \dar["\text{pinch}"]\\
M\vee M\vee M\rar{(\lambda_1,\lambda_2, \lambda_3)} & N \rar & X \rar& \Sigma M\vee\mathrlap{\Sigma M\vee \Sigma M}
\end{tikzcd}

\end{document}


• Nice being not too wide +1 – Happy May 17 at 13:43

Add the option equal for the arrow.

However, the diagram is very wide already with standard column separation, so using sep=large will make it too wide.

I suggest to widen only the first arrow in the bottom row which can be accomplished with &[2em] in the first row. Using row sep=large will somehow balance the whole thing.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz-cd}
\begin{document}

$\begin{tikzcd}[row sep = large] % top row &[2em] % some more length for the first arrow & \Sigma M \arrow[r,equal] \arrow[d,"f"'] & \Sigma M \arrow[d,"\mathrm{pinch}"] \\ % bottom row M \vee M \vee M \arrow[r,"{(\lambda_1,\lambda_2,\lambda_3)}"] & N \arrow[r] & X \arrow[r] & \Sigma M \vee \Sigma M \vee \Sigma M \end{tikzcd}$

\end{document}