12 setfontsize
-1.5 1.5 setxrange
-4 4 setyrange

50 setxunit
[1 1 .5 .5 .1 .1] {orange} Quadrillage
.7 setlinewidth

/f {
   argtanh
} def

/unites {} def
tracerepere
marks

gsave
   1.5 setlinewidth
   vert
   1 verticale droite
   -1 verticale droite
   bleu
   -.9999 .9999 {f} Courbe
grestore

<tex>
$$
   y = {\rm Arg\ th}\,  x
$$
</tex>

3 setdboxit
/linearc .05 def
/fillstyle {jaune fill} def
boxit
-.2 2 [1.7 dup] cctexlabel

2.5 settailletangente
0 {f} tangente

#tex# $x=1$
1 -3.5 cltexlabel
#tex# $x=-1$
-1 3.5 crtexlabel

setTimesItalic
   (O) O drtext