theorem Th31:
  for i for R being Element of i-tuples_on REAL holds mlt(i|->1,R) = R
proof
  let i;
  let R be Element of i-tuples_on REAL;
  thus mlt(i|->1,R) = 1*R by RVSUM_1:63
    .= R by RVSUM_1:52;
end;
