
Dans un repère, quel qu'il soit, pour lire les coordonnées d'un point, il faut tracer les parallèles aux axes passant par ce point.

\begin{center}
\begin{tikzpicture}[>=latex,xslant=0.4,yslant=0.2]
\draw[gray!50,dashed] (-5,-5) grid (5,5);
\draw[thick,->] (-5,0) -- (5,0);
\draw[thick,->] (0,-5) -- (0,5);
\draw[red,very thick] (0,0) node[below left] {$O$} -- (1,0) node[below] {$I$};
\draw[red,very thick] (0,0) -- (0,1) node[left] {$J$};
\fill[purple] (3,-1) circle (1pt) node[below right] {A\coord{3}{-1}};
  \draw[dotted,thick,green!50!black] (0,-1) node[left] {$-1$} -- (3,-1) -- (3,0) node[above] {$3$};
\fill[purple] (-4,-3) circle (1pt) node[below right] {B\coord{-4}{-3}};
	\draw[dotted,thick,pink!50!black] (0,-3) node[right] {$-3$} -- (-4,-3) -- (-4,0) node[above] {$-4$};
\fill[purple] (-1,4) circle (1pt) node[above left] {C\coord{-1}{4}};
	\draw[dotted,thick,violet] (0,4) node[right] {$4$} -- (-1,4) -- (-1,0) node[below] {$-1$};
\fill[purple] (-2,-1) circle (1pt) node[below] {D\coord{-2}{-1}};
	\draw[dotted,thick,yellow!50!black] (0,-1) -- (-2,-1) -- (-2,0) node[above] {$-2$};
\fill[purple] (2,3) circle (1pt) node[above right] {E\coord{2}{3}};
	\draw[dotted,thick,brown] (0,3) node[left] {$3$} -- (2,3) -- (2,0) node[below] {$2$};
\end{tikzpicture}
\end{center}