reserve x,y,c for set;

theorem
  for x,y,c being non pair set for s being State of BorrowCirc(x,y,c)
for a1,a2 being Element of BOOLEAN st a1 = s.x & a2 = s.y holds Following(s,2).
  [<*x,y*>,and2a] = 'not' a1 '&' a2
proof
  let x,y,c be non pair set;
  reconsider a = c as Vertex of BorrowStr(x,y,c) by Th6;
  let s be State of BorrowCirc(x,y,c);
  s.a is Element of BOOLEAN;
  hence thesis by Lm2;
end;
