答案1
答案2
感谢猫@SchrodingersCat 的 tikz
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,calligraphy}
\begin{document}
\begin{center}
\begin{tikzpicture}[x=2cm]
\draw (-1,0) -- (4,0);
\path foreach \X/\Y/\Z in
{0/a_0/a_1, pi/b_0/, {pi/2}/b_1/b_2,{pi/4}/a_2/a_2}
{ (\X,0) node[circle,fill,inner sep=0.5mm,
label=above:{$\Y$},label=below:{$\Z$},alias=\Z] (\Y) {}};
\begin{scope}[thick,decoration={calligraphic brace, amplitude=6pt}]
\draw[decorate] (current bounding box.north) coordinate (aux)
(a_2|-aux) -- node[above=1ex]{$I_2$} (b_1|-aux);
\draw[decorate] (current bounding box.south) coordinate (aux)
(b_1|-aux) -- node[below=1ex]{$I_1$} (a_0|-aux);
\draw[decorate] (current bounding box.south) coordinate (aux)
(b_0|-aux) -- node[below=1ex]{$I_0$} (a_0|-aux);
\end{scope}
\end{tikzpicture}
\end{center}
\end{document}