1 setxyrapport
25 setxunit
7.5 setborder
-30 30 setxrange
-30 30 setyrange
jpegmode
/a 12 def
/b 1 def
/c 3 def
/resolution 500 def
      
/quadrillagegray 0.4 def
1 setquadrillagexstep
1 setquadrillageystep
quadrillage
2 2 settkstep
1 1 setsubtkstep
2 2 setmkstep
traceaxes
1.75 setlinewidth
continu
rouge
/X {settvar
#rpn#   (a+b)*Cos(t)-c*Cos((1+a/b)*t)
} def
/Y {settvar
#rpn#   (a+b)*Sin(t)-c*Sin((1+a/b)*t)
} def
 0 2 pi mul  {X} {Y} Courbeparam