Source — Euclid's Elements, encoded as an rrxiv paper

1% fig-i-1.tex — I.1: equilateral triangle on a given segment.
2\begin{figure}[H]
3\centering
4\begin{tikzpicture}[scale=1.2, line cap=round]
5  \coordinate (A) at (0,0);
6  \coordinate (B) at (2,0);
7  \coordinate (C) at (1,{sqrt(3)});
8  % Two circles, centres A and B, radius AB.
9  \draw[thin] (A) circle (2);
10  \draw[thin] (B) circle (2);
11  % Triangle.
12  \draw[very thick] (A) -- (B) -- (C) -- cycle;
13  % Labels.
14  \node[below left]  at (A) {$A$};
15  \node[below right] at (B) {$B$};
16  \node[above]       at (C) {$C$};
17\end{tikzpicture}
18\caption{Proposition I.1. The two circles with centres $A$ and $B$ and
19common radius $AB$ meet at $C$; the triangle $ABC$ is equilateral.}
20\label{fig:I.1}
21\end{figure}
22