10 setxunit 7.5 setborder -10 10 setxrange -10 10 setyrange jpegmode /a 1.55 def /b 2.55 def /c 3 def /resolution 500 def 2 2 settkstep 1 1 setsubtkstep 2 2 setmkstep ticks traceaxes axesarrow unites /X {settvar a b add t Cos mul c t 1 a b div add mul Cos mul sub } def /Y {settvar a b add t Sin mul c t 1 a b div add mul Sin mul sub } def gsave .75 setlinewidth continu bleu 0 20 pi mul {X} {Y} Courbeparam grestore