绘制笛卡尔图

Question

我想在下图的右边正方形中绘制一个矩形：

生成该图像的代码如下：

\documentclass[
paper=a4,
fontsize=12pt,
titlepage,
%draft,
%twoside,
final
]{article}
\usepackage{tikz-cd}
\begin{document}

Let $\mathcal{C}$ be a category and let
\begin{equation*} 
    \begin{tikzcd} 
        X'' \ar[r,] \ar[d,] &  X' \ar[d]\ar[r]  & X\ar[d]  \\
        S'' \ar[r]& S' \ar[r] & S
    \end{tikzcd}
\end{equation*}
    be a diagram in $\mathcal{C}$. 
    
\end{document}

我们怎样才能做到这一点？

Answer 1

我在图表的右侧正方形内画了一个矩形。

\documentclass[
paper=a4,
fontsize=12pt,
titlepage,
%draft,
%twoside,
final
]{article}
\usepackage{tikz-cd}
\usepackage{amsmath,amssymb}
\begin{document}

Let $\mathcal{C}$ be a category and let
\begin{equation*} 
    \begin{tikzcd} 
        X'' \ar[r] \ar[d] &  X' \ar[d] \ar[dr, phantom, "\square"] \ar[r] & X\ar[d]  \\
        S'' \ar[r]& S' \ar[r] & S
    \end{tikzcd}
\end{equation*}
    be a diagram in $\mathcal{C}$. 
    
\end{document}