theorem
  for p being FinSequence of REAL st len p = 3 holds
  p is 3-element FinSequence of REAL
  proof
    let p being FinSequence of REAL;
    assume len p = 3;
    then p = <* p.1,p.2,p.3 *> by FINSEQ_1:45;
    hence thesis;
  end;
