prologues := 2 ;
defaultfont := "cmr10" ;

beginfig(1)

    path t ;

    t = (0,0) -- (-30,-100) -- (30,-100) -- cycle ;
    fill t withcolor 0.8 white ;
    draw t ;

    draw (0,0) withpen pencircle scaled 5pt ;

    label(btex $B_n$ etex,center t) ;

    picture triangle ;

    triangle = currentpicture ;

    draw triangle shifted (-50,-50) ;

    draw (0,0) -- (-50,-50) ;

endfig ;

beginfig(2)

    picture bino[] ;

    def width(expr p) =
        xpart (lrcorner p - llcorner p)
    enddef ;

    bino[1] = nullpicture ;

    addto bino[1] doublepath (0,0) withpen pencircle scaled 5pt ;
    addto bino[1] doublepath (0,0) -- (0,-50) ;
    addto bino[1] doublepath (0,-50) withpen pencircle scaled 5pt ;

    for i = 2 upto 6 :
        bino[i] = bino[i - 1] ;
        addto bino[i] also (bino[i - 1] shifted (-width(bino[i-1]),0) shifted (-10,-50)) ;
        addto bino[i] doublepath (0,0) -- ((- 10,-50) shifted (-width(bino[i-1]),0)) ;
    endfor

    draw bino[4] rotated -90 ;
    draw (bino[6] shifted (width(bino[6]),0) shifted (20,0)) rotated -90 ;

endfig ;

end