答案1
这绘制了两个边界摆线。
\documentclass[tikz,border=3.14mm]{standalone}
\begin{document}
\begin{tikzpicture}[scale=2.5]
\draw (-4,0) -- (4,0) (0,2.5) -- (0,-2.5);
\draw plot[domain=-pi:pi,samples=51,smooth] ({\x - sin(\x r)},{cos(\x r)+1});
\draw plot[domain=0:2*pi,samples=51,smooth] ({\x - pi - sin(\x r)},{cos(\x r)-1});
\draw foreach \X in {0.75,1,1.25,1.5}
{(0,-2+\X) circle[radius=\X]};
\end{tikzpicture}
\end{document}