reserve a,b,c,d,m,x,n,j,k,l for Nat,
  t,u,v,z for Integer,
  f,F for FinSequence of NAT;
reserve p,q,r,s for real number;
reserve a,b,c,d,m,x,n,k,l for Nat,
  t,z for Integer,
  f,F,G for FinSequence of REAL;
reserve q,r,s for real number;
reserve D for set;

theorem
  n+1 = len f implies (f/^n) = <*f.(n+1)*>
  proof
    assume n+1 = len f; then
    (f|n)^<*f.(n+1)*> = f by RFINSEQ:7
    .= (f|n)^(f/^n) by RFINSEQ:8;
    hence thesis by FINSEQ_1:33;
  end;
