autocrop
-.2 5 setxrange
-.5 1.2 setyrange

0 5 setxrange
0 1.2 setyrange

50 setxunit
100 setyunit

/t .6 def
/lambda 1 def
/f {
   lambda mul neg Exp lambda mul   
} def

/fillstyle {.6 setgray fill} def
t xmax {f} Fillcourbe
.3 setlinewidth
[t 0 t dup f] ligne
1 setlinewidth 
0 xmax {f} Courbe

%marks
traceaxes
axesarrow
0 xmark
lambda ytick

setTimesItalic
   (y) 0 ymax drtext
   (t) xmax 0 dltext
setSymbol
   (l) 0 lambda cltext

<tex>
$t_0$
</tex>
t 0 dctexlabel

<tex>
$y = f (t)$
</tex>
1.5 dup f urtexlabel

/F' {t 2 div .11} def
/F {t 2 div -.1} def
<tex>
$F (t_0)$
</tex>
F dctexlabel

[F F'] (->) ligne

/R' {1.5 .11} def
/R {1.5 -.1} def
<tex>
$R (t_0)$
</tex>
R dctexlabel

[R R'] (->) ligne