\begin{pspicture}*(-10,-5)(10,10) \psgrid[griddots=10, gridcolor=gray, subgriddiv =0](-10,-5)(10,10) \psdot(-3,-2) \uput[d](-3,-2){$A$} \psdot(0,3) \uput[u](0,3){$B$} \psdot(4,-1) \uput[d](4,-1){$C$} %\psline[arrowsize=4pt 3]{->}(-5,1)(1,2) %\uput[u](-2,1.5){$\vec{AB}$} %\psline[arrowsize=4pt 3]{->}(-5,1)(-1,-2) %\uput[dl](-3,-0.5){$\vec{AC}$} %\psline[arrowsize=4pt 3]{->}(-5,1)(5,-1) %\uput[u](0,0){$\vec{AD}$} \end{pspicture}