\usepackage{tikz}
\begin{tikzpicture}[scale=0.4]
\draw (0,0) circle (sqrt{20});
\draw (0,0) node{$\bullet$} -- (4,2);
\draw (2,6)-- (6,-2);
\draw (-0.5,-0.5) node{$O$} ;
\draw (4.5,2) node{$A$} ;
\draw (-4.5,2) node{$\mathcal{C}$} ;
\draw (3.55,1.78) -- (3.78,1.33) -- (4.22,1.55);
\end{tikzpicture}
\begin{tikzpicture}[scale=1]
\draw (0,0) circle (sqrt{20});
\draw (0,0) node{$\times$};
\draw (-0.5,-0.5) node{$O$};
\draw (-4.5,2) node{$\mathcal{C}$} ;
\draw (10,0) node{$\times$};
\draw (10.8,0) node{$M$};
\draw (0,0) -- (10,0);
\draw[dashed] (6.062,3.5) arc (30:60:7);
\draw[dashed] (3.938,3.5) arc (150:120:7);
\draw[dashed] (6.062,-3.5) arc (-30:-60:7);
\draw[dashed] (3.938,-3.5) arc (-150:-120:7);
\draw (5,6)-- (5,-6);
\draw (5.8,-0.5) node{$I$};
\draw (5,0) circle (5);
\draw (0,5) -- (10,0);
\end{tikzpicture}
\begin{tikzpicture}
\draw (0,0) -- (4,0) -- (5,3) -- (1,3) -- cycle;
\draw (0,0) -- (5,3);
\draw (1,3) -- (-3,3);
\draw (1,3.5) node{$C$};
\draw (5,3.5) node{$B$};
\draw (4,-0.5) node{$D$};
\draw (0,-0.5) node{$E$};
\draw (-3,3) node{$\bullet$} +(0,0.5) node{$A$};
\draw (1.66,1) node{$\bullet$} +(0.5,-0.1) node{$F$};
\draw (3.33,2) node{$\bullet$};
\end{tikzpicture}
\begin{tikzpicture}
\draw (0,0) -- (6,0) -- (2,4) -- cycle;
\draw (2,4) -- (2.4,4.8);
\draw (1.8,4.3) node{$C$};
\draw (6,-0.5) node{$B$};
\draw (0,-0.5) node{$A$};
\draw (0.5,1) node{$\bullet$};
\draw (1,2) node{$\bullet$};
\draw (1.5,3) node{$\bullet$};
\draw (2.5,5) node{$\bullet$} +(0,0.5) node{$J$};
\draw (2.67,3.33) node{$\bullet$} +(0.5,0) node{$K$};
\draw (3.33,2.67) node{$\bullet$};
\draw (4,2) node{$\bullet$};
\draw (4.67,1.33) node{$\bullet$};
\draw (5.33,0.67) node{$\bullet$};
\draw (3,0) node{$\bullet$} +(0,0.5) node{$I$};
\draw (1.5,0) node{$||$} (4.5,0) node{$||$};
\end{tikzpicture}\\