[Tex/LaTex] How to draw a circle with a triangle in TikZ

circlesdiagramsnodestikz-pgf

Be sorry that I cannot provide the coordinates of all points, or I can draw the picture. How can I make this figure? Thanks for any help!

enter image description here

Best Answer

In this case it is pretty simple to use the calc and intersections library:

\documentclass[tikz,border=0.125cm]{standalone}

\usetikzlibrary{calc,intersections}

\begin{document}

\begin{tikzpicture}

\path [rotate=60]
  (0,0)   coordinate (A) 
  (-2,-3) coordinate (B) 
  (0,-3)  coordinate (C)
  ($(B)!2!(C)$)   coordinate (D)
  ($(A)!0.5!(B)$) coordinate (O);

\path [name path=first]  (A) -- (D);
\path [name path=second] (C) -- ($(C)!1!-90:(O)$);

\path [name intersections={of=first and second}]
 (intersection-1) coordinate (E);

\draw (A) -- (B) -- (C) -- (D) -- cycle;
\draw let \p1=(A), \p2=(O), \n1={veclen(\x2-\x1,\y2-\y1)} in (O) circle [radius=\n1];
\draw (A) -- (C);
\draw (C) -- (E);

\foreach \p/\a in {A/above,O/left,B/below,C/right,D/right,E/above}
  \node [inner sep=1pt, circle, fill, label=\a:\p] at (\p) {};

\end{tikzpicture}

\end{document}

enter image description here

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