\begin{figure}[htb]
	\centering

\begin{tikzpicture}
	
	\draw[-latex] (-0.5,0) -- (7,0) node[below] {$x$};
	\draw[-latex] (0,-0.5) -- (0,6) node[left] {$y$};
	
	\coordinate[] (A) at (4,3);
	
	\draw[] (A) circle [radius=1.5];
	
	\draw[]  (A) to ["$r$",sloped] ++ (45:1.5)  coordinate[] (B) ;
	\draw[]  (B) to [] ++ (270:{sqrt(1.125)})  coordinate[] (C);
	\draw  (C) to (A);
	\draw[fill=black] (A) circle (0.05);
	\draw[fill=black] (B) circle (0.05);
	
	\draw[dashed] (A) -- (4,-0.1) node[yshift=-2mm]{$x_m$};
	\draw[dashed] (A) -- (-0.1,3) node[xshift=-3mm]{$y_m$}; 
	
	\draw[dashed] (C) -- (4+1.06066,-0.1) node[yshift=-2mm]{$x$}; 
	\draw[dashed] (B) -- (-0.1, 4.06066) node[xshift=-3mm]{$y$}; 
	
	\draw[latex-latex] (4,2.4) -- (5.106066, 2.4) node [midway, below   ]{$a$} ;
	
	\draw[latex-latex] (2,3) -- (2, 4.06066) node[midway, left]{$b$};    
	
	\draw pic["$\cdot$", draw, angle radius=3mm ] {angle=B--C--A};
\end{tikzpicture}

\caption{Kreis mit Mittelpunkt $M\left(x_{m}, y_{m}\right)$ und Radius $r$.}
\end{figure}

