reserve ADG for Uniquely_Two_Divisible_Group;
reserve a,b,c,d,a9,b9,c9,p,q for Element of ADG;
reserve x,y for set;

theorem Th8:
  a,b ==> c,c implies a=b
proof
  assume a,b ==> c,c;
  then a # c = b # c by Th5;
  hence thesis by RLVECT_1:8;
end;
