TikZ and figures

% Drawing a circle in the complex plane % Author: Martin Scharrer 

\documentclass{article} 

\usepackage{tikz} 

\begin{document} 

    \begin{tikzpicture}     

        \begin{scope}[thick,font=\scriptsize]     

            % Axes:     

            % Are simply drawn using line with the `->` option to make them arrows:     

            % The main labels of the axes can be places using `node`s:     

            \draw [->] (-5,0) -- (5,0) node [above left]  {$\Re\{z\}$};     

            \draw [->] (0,-5) -- (0,5) node [below right] {$\Im\{z\}$};      

            % Axes labels:     

            % Are drawn using small lines and labeled with `node`s. The placement can be set using options     

            \iffalse

                % Single     

                % If you only want a single label per axis side:     

                \draw (1,-3pt) -- (1,3pt)   node [above] {$1$};     

                \draw (-1,-3pt) -- (-1,3pt) node [above] {$-1$};     

                \draw (-3pt,1) -- (3pt,1)   node [right] {$i$};     

                \draw (-3pt,-1) -- (3pt,-1) node [right] {$-i$};     

            \else

                % Multiple     

                % If you want labels at every unit step:     

                \foreach \n in {-4,...,-1,1,2,...,4}{%         

                    \draw (\n,-3pt) -- (\n,3pt)   node [above] {$\n$};         

                    \draw (-3pt,\n) -- (3pt,\n)   node [right] {$\n i$};     }     

            \fi     

        \end{scope}     

        % The circle is drawn with `(x,y) circle (radius)`     

        % You can draw the outer border and fill the inner area differently.     

        % Here I use gray, semitransparent filling to not cover the axes below the circle     

        \path [draw=none,fill=gray,semitransparent] (+1,-1) circle (3);     

        % Place the equation into the circle:     

        \node [below right,darkgray] at (+1,-1) {$|z-1+i| \leq 3$}; 

    \end{tikzpicture} 

\end{document}