Re: tikz intersezione retta circonferenza

`\usetikzlibrary{shapes,arrows,trees,positioning,through}
\usetikzlibrary{calc}
\def\raggio{2cm};
\begin{tikzpicture}
\coordinate [label=$C$] (C) at (0,0);
\node (D) at (1,2) {};
\coordinate [label=$D$] (D) at (1,2);
\draw (C)[draw] circle (\raggio);
\draw (C) – – ($ (C)!\raggio!(D) $);
\draw (0,0);
\end{tikzpicture}`

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