reserve x,y,z,X,Y for set;
reserve X,Y for non empty set,
  f for Function of X,Y;
reserve X, Y for non empty set,
  F for (BinOp of Y),
  B for (Element of Fin X),
  f for Function of X,Y;
reserve A for set,
  x,y,z for Element of Fin A;
reserve X,Y for non empty set,
  A for set,
  f for (Function of X, Fin A),
  i,j,k for (Element of X);

theorem Th44:
  FinUnion({}.X,f) = {}
proof
  FinUnion A is commutative & FinUnion A is associative by Th35,Th36;
  hence FinUnion({}.X,f) = the_unity_wrt FinUnion A by Th28,Th38
    .= {} by Th40;
end;
