25 setxunit
7.5 setborder
-8 8 setxrange
-8 8 setyrange
jpegmode
/a 6 def
/b 2 def
/c 0.75 def

2 2 settkstep
1 1 setsubtkstep
2 2 setmkstep
ticks
traceaxes
axesarrow
0.75 setlinewidth
continu
bleu
/X {settvar
#rpn#   a*(cos(t))+c*cos((a-b)*t/b)
} def
/Y {settvar
#rpn#   (a-b)*sin(t)-c*sin((a-b)*t/b)
} def
 0 300 pi mul  {X} {Y} Courbeparam