Code for http://math.stackexchange.com/a/1634348/290189

mse1634312.tex

\documentclass[tikz]{standalone}
\begin{document}
\begin{tikzpicture}
  \draw [fill] (0,0) circle [radius = 0.025];
  \node [below] at (0,0) {$x$};
  \draw (0,0) circle (1);
  \draw (0,0) -- (120:1) node[pos=0.5,above] {$r$};
  \draw [fill] (2,2) circle [radius = 0.025];
  \node [below] at (2,2) {$y$};
  \draw (2,2) circle (0.7);
  \draw (2,2) -- ++(120:0.7) node[pos=0.5,above] {$\varepsilon$};
  \draw (0,0) -- (2,2);
  \draw [fill] (2.3,2.3) circle [radius = 0.025];
  \node [below] at (2.3,2.3) {$z$};
\end{tikzpicture}
\end{document}