10.9.25 Section



  \begin{texgraph}[name=Section, export=pgf]
  view(-2,3,-2.5,3), Marges(0,0,0,0), size(7.5),
  cube:=Parallelep(Origin,3*vecI,3*vecJ,3*vecK),
  plan:=[M(3,0,0),-vecI-vecK/2],
  S:=Section(plan, cube), FillStyle:=full,
  FillColor:=firebrick, HideWidth:=8,
  DrawPoly(S,4)
  \end{texgraph}

 PIC



Section