-4 5 setxrange
-2 4 setyrange
20 setxunit

traceOx

%xticks
0 xtick
[0 ] {xmark} apply

/A{-3.3 0} def   
/B {3 0} def
/C{-3 -0.3} def   
/D{3 -0.3} def  
/E{2 2.5} def 
/F{-2 2.5} def 
1.7 setlinewidth
rouge
[A B] ([-]) ligne
<tex>
$$
  1- \sqrt{2}
$$
</tex>

%% exemple 1 : simple
C dctexlabel 

<tex>
$$
 \sqrt{2}-1
$$
</tex>
D dctexlabel 
 setTimesItalic
   () C dltext
   () B drtext
  bleu
/arrowscale {2 dup} def
/angleA 60 def
/angleB 120 def
0 0.5 3 0.5 (->) pccurve

%/arrowscale {2 dup} def
/angleA 60 def
/angleB 120 def
-3 0.5 0 0.5 (<-) pccurve
vert
<tex>
$$
 \sqrt{2}-1
$$
</tex>
E dctexlabel 
<tex>
$$
 \sqrt{2}-1
$$
</tex>
F dctexlabel