25 setxunit 7.5 setborder 90 setangle_repere -5 5 setxrange -5 5 setyrange 1 1 settkstep .5 .5 setsubtkstep 2 2 setmkstep ticks subticks marks traceaxes axesarrow 0 2 pi mul settrange /a 2 def /h 0 def /rho { Cos a mul h add } def /dessin { {settvar t Cos t rho mul} {settvar t Sin t rho mul} courbeparam } def 1.75 setlinewidth continu bleu dessin pointilles /h 1 store dessin dotted /h 2 store dessin