
theorem Th84:
  for C1,C2 being Coherence_Space for x,y being set holds x U+ y
  in C1 "/\" C2 iff x in C1 & y in C2
proof
  let C1,C2 be Coherence_Space, x,y be set;
  now
    given a being Element of C1, b being Element of C2 such that
A1: x U+ y = a U+ b;
    take a,b;
    thus x = a & y = b by A1,Th80;
  end;
  hence thesis;
end;
