40 setxunit
7.5 setborder
90 setangle_repere
-5 6 setxrange
-1 3 setyrange
1 1 settkstep
.5 .5 setsubtkstep
2 2 setmkstep
ticks
subticks
marks
traceaxes
axesarrow
/R {settvar
#rpn#   1+Tan(t/2)
} def
  3 neg  3 settrange
gsave
   1 setlinewidth
   continu
   bleu
   (R) courbepolar
grestore
noir
.5 setlinewidth
0 2 1 2 droite
1.75 setlinewidth
[0 -1 0 1] (<->) ligne