reserve i,j,k,n for Nat;
reserve D for non empty set,
  p for Element of D,
  f,g for FinSequence of D;

theorem
  f is non empty implies f = <*f/.1*>^(f/^1)
proof
  assume A1: f is non empty; then
A2:  1 in dom f by Th6;
  f|1 = <*f.1*> by A1,Th20
     .= <*f/.1*> by A2,PARTFUN1:def 6;
  hence thesis by RFINSEQ:8;
end;
