reserve a,b,m,x,y,i1,i2,i3,i for Integer,
  k,p,q,n for Nat,
  c,c1,c2 for Element of NAT,
  z for set;

theorem Th2:
  for X being real-membered set, a being Real holds card X = card (a ++ X)
by Th1,CARD_1:5;
