答案1
答案2
tikz-cd
可以奏效
\documentclass{standalone}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}[column sep=0.4cm,row sep=0.4cm]
& & a \arrow[d,equal] & \\
& & b \arrow[rd,dash]\arrow[ld,dash] & \\
& b \arrow[rd,equal]\arrow[ld,dash] & & * \arrow[d,equal] \\
b \arrow[d,dash] & & c & c\\
c & & &
\end{tikzcd}
\end{document}