答案1
欢迎!这是一个开始。
\documentclass[tikz,border=3mm]{standalone}
\begin{document}
\begin{tikzpicture}[Dotted/.style={% https://tex.stackexchange.com/a/52856/194703
line width=1.5pt,
dash pattern=on 0.001\pgflinewidth off #1,line cap=round,
shorten <=#1},Dotted/.default=6pt,
bullet/.style={circle,fill,inner sep=1pt}]
\draw (0,0) -- ++(2,0) node[bullet](X){}
foreach \X in {60,40,-60} { (X) ++ (\X:2) node[bullet]{} edge (X)};
\draw[Dotted] (X) ++ (60:2.2) arc[start angle=60,end angle=-60,radius=2.2]
node[midway,fill=white]{$a$};
\draw (0,-4.5) -- ++(2,0) node[bullet](X'){}
foreach \X in {60,40,-60} { (X') ++ (\X:2) node[bullet]{} edge (X')};
\draw[stealth-stealth] (X') ++ (60:2.2)
arc[start angle=60,end angle=-60,radius=2.2] node[midway,fill=white]{$a$};
\end{tikzpicture}
\end{document}
将来请尝试发布一些代码。否则其他人必须猜测一切,如果您展示您尝试过的内容,您将从问题中受益更多。