% This picture represents the unit complex circle
% (C) Thiago Brevidelli
\begin{tikzpicture}[scale=1.2]
  \node[above] (O) at (0,1) {$i$};
  \node[right] (O) at (1,0) {$1$};
  \filldraw[black] (0, 1) circle (1pt);
  \filldraw[black] (1, 0) circle (1pt);
  \draw (0, 0) circle (1);
\end{tikzpicture}

