20 setxunit
10 setborder
-10 10 setxrange
-10 10 setyrange
jpegmode
/a 2 def
/b 1 def
/c 2 def
/resolution 500 def
      
1 1 settkstep
1 1 setsubtkstep
2 2 setmkstep
ticks
marks
traceaxes
axesarrow
unites
0.75 setlinewidth
continu
bleu
/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