\begin{exercice}Sur la figure ci-dessous, le cercle $\mathcal C$ est le cercle \\trigonométrique de centre $O$ et d'origine $C$.  

Quel est le réel associé au point $A$ sur ce cercle?

\begin{center}
 \begin{tikzpicture}[general,scale=2]
% \draw [quadrillage, xstep=0.1, ystep=0.1] (-3,-3)grid (1,1);
   \draw (0,0) circle (1);
  \draw (-1.7,0) circle (0.7);
  \draw (-2.4,0)--(1,0);
  \draw (-2.4,0)--(1,0);
  \draw (-2.4,0) node[left] {$E$};
  \draw (1,0) node[right] {$C$};
  \draw (0,0) node[below] {$O$};
  \draw (0.87,0.5) node[above right] {$A$};
  \draw (-1,0) node[below right] {$B$};
  \draw (-2.3,-0.35) node[below left] {$G$};
  \draw (-1.7,0.7) node[above] {$F$};
  \draw (0.71,0.71) node[above right] {$({\cal C})$};
  \draw[color=C1] (-1.75,0.3) node {\bfseries15\degre};
  \draw (0.87,0.5)--(0,0);
  \draw (0.87,0.5)--(-2.3,-0.35)--(-1.7,0.7)--(-2.4,0);
  \draw[epais, color=C1] (-2,0.4) arc (225:240:0.42);
 \end{tikzpicture}
 \end{center}
\end{exercice}

