25 setxunit
7.5 setborder
90 setangle_repere
-5 5 setxrange
-5 5 setyrange
1 1 settkstep
.5 .5 setsubtkstep
2 2 setmkstep
ticks
subticks
marks
traceaxes
axesarrow
/R {settvar
#rpn#   2*Cos(2*t)-3*Cos(t)
} def
 0 10 pi mul  settrange
gsave
   .75 setlinewidth
   continu
   bleu
   (R) courbepolar
grestore