reserve X for non empty set,
  S for SigmaField of X,
  M for sigma_Measure of S,
  f,g for PartFunc of X,ExtREAL,
  E for Element of S;

theorem Th7:
  for r be Element of ExtREAL holds Product (<*r*>) = r
proof
  let r be Element of ExtREAL;
  reconsider r9 = r as Element of ExtREAL;
  reconsider F = <*r9*> as FinSequence of ExtREAL;
  multextreal $$ F = r by FINSOP_1:11;
  hence thesis by Def2;
end;
