\def\F{x 180 mul 3.1415926 div cos 2 mul}
\pstGeonode(0.3,-1){O}(2,.5){M}
\ncline[linecolor=blue, arrowscale=2]{->}{O}{M}
\psaxes{->}(0,0)(-3,-3)(3,4)
\psplot[linewidth=2\pslinewidth, 
        linecolor=gray]{-3.14}{3.14}{\F}
\psset{PointSymbol=*}
\pstCircleOA{O}{M}
\psset{PointSymbol=o}
\pstInterFC{\F}{O}{M}{1}{N_0}
\pstInterFC{\F}{O}{M}{-1}{N_1}
\pstInterFC{\F}{O}{M}{-2}{N_2}
\pstInterFC{\F}{O}{M}{2}{N_3}
