25 setxunit 7.5 setborder 90 setangle_repere -3.1 3.1 setxrange -3.1 3.1 setyrange 1 1 settkstep .5 .5 setsubtkstep 2 2 setmkstep ticks ysubticks marks traceaxes axesarrow /R {settvar #rpn# 1+2*Cos(3*t) } def 0 6 pi mul 3 div settrange gsave 0.75 setlinewidth continu noir (R) courbepolar grestore