15 setxunit
5 setborder
-20 20 setxrange
-20 20 setyrange
jpegmode
/a 6.16 def
/b 3.08 def
/c 5.75 def
/resolution 500 def
      
/quadrillagegray 0.4 def
1 setquadrillagexstep
1 setquadrillageystep
quadrillage
1 1 settkstep
1 1 setsubtkstep
2 2 setmkstep
ticks
subticks
marks
traceaxes
axesarrow
unites
1.75 setlinewidth
continu
noir
/X {settvar
#rpn#   (a+b) * Cos (t) - c * Cos (t*(1+a/b))
} def
/Y {settvar
#rpn#   (a+b) * Sin (t) - c * Sin (t*(1+a/b))
} def
 0 20 pi mul  {X} {Y} Courbeparam