[
    view(-7,7,-7,7), Marges(0,0,0,0), size(12,1), background(full,beige),
    H:=5, R:=4, a:=2, Plan:=[M(a,0,0),vecI],
    C1:=cone(Origin, H*vecK,R,45), C2:=cone(Origin, -H*vecK,R,45),
    L1:=Intersection(Plan,C1), L2:=Intersection(Plan,C2),
    Asymp1:=getdroite( [M(a,0,0),M(0,R,H)] ),
    Asymp2:=getdroite( [M(a,0,0),M(0,-R,H)] ),

    Build3D([1, Rgb(0.74,1,0.73)+0.9*i,getplan(Plan)],
        [1, Rgb(0.73,0.74,1),C1,C2],
        [2,darkgreen,12, Asymp1,Asymp2],
        [2,0,8,axes3d()],
       ),
    Display3D(),

    Color:=red, Width:=8, DrawAretes([L1,L2],0), Color:=black,
    Arrows:=1, LineStyle:=dotted, Axes3D(0,0,0)
]