
theorem ConstantSum:
  for f being non empty constant real-valued FinSequence holds
    Sum f = (the_value_of f) * (len f)
  proof
    let f be non empty constant real-valued FinSequence;
    set r = the_value_of f, i = len f;
    f = (dom f) --> r by FUNCOP_1:80
     .= i |-> r by FINSEQ_1:def 3;
    hence thesis by RVSUM_1:80;
  end;
