\psset{xunit=3, yunit=.4} \begin{pspicture}(0,-1)(3,20)\psgrid \psplot[linewidth=4\pslinewidth, linecolor=green]{0}{3}{2.71828182846 x exp} \psplotequadiff[linecolor=magenta, plotpoints=16]{0}{3}{1}{} \psplotequadiff[linecolor=blue, plotpoints=151]{0}{3}{1}{} \psplotequadiff[linecolor=red, method=rk4, plotpoints=15]{0}{3}{1}{} \psplotequadiff[linecolor=Orange, method=rk4, plotpoints=4]{0}{3}{1}{} \psset{linewidth=2\pslinewidth} \rput*(3.3,19){\psline[linecolor=magenta](-.75cm,0)} \rput*[l](3.3,19){\small\textsc{Euler} ordre 1 $h=0{,}2$} \rput*(3.3,17){\psline[linecolor=blue](-.75cm,0)} \rput*[l](3.3,17){\small\textsc{Euler} ordre 1 $h=0{,}02$} \rput*(3.3,15){\psline[linecolor=red](-.75cm,0)} \rput*[l](3.3,15){\small RK ordre 4 $h=0{,}2$} \rput*(3.3,13){\psline[linecolor=Orange](-.75cm,0)} \rput*[l](3.3,13){\small RK ordre 4 $h=1$} \rput*(3.3,11){\psline[linecolor=green](-.75cm,0)} \rput*[l](3.3,11){\small solution exacte} \end{pspicture}