15 setxunit 5 setborder -20 20 setxrange -20 20 setyrange jpegmode /a 10 def /b 5 def /c 0 def /resolution 500 def /quadrillagegray 1 def 10 setquadrillagexstep 10 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