/width 175 def
/height 175 def
/border 7.5 def
/xmin -1.5 def
/xmax 1.5 def
/ymin -1.5 def
/ymax 1.5 def
jpegmode
/xtkstep 1 def
/ytkstep 1 def
/xsubtkstep .5 def
/ysubtkstep .5 def
/xmkstep 2 def
/ymkstep 2 def
/R {settvar
    5 t mul 4 div Cos 1 3 div add
} def
  0  8 pi mul settrange
gsave
   thin setcurvelinewidth
   continu
   bleu
   (R) courbepolar
grestore