reserve x,y,z for set;
reserve f,f1,f2,f3 for FinSequence,
  p,p1,p2,p3 for set,
  i,k for Nat;
reserve D for non empty set,
  p,p1,p2,p3 for Element of D,
  f,f1,f2 for FinSequence of D;

theorem Th80:
  <*>D/^k = <*>D
proof
  per cases;
  suppose
    k = 0;
    hence thesis;
  end;
  suppose
    k > 0;
    then k > len <*>D;
    hence thesis by RFINSEQ:def 1;
  end;
end;
