
theorem
  for S be finite set, s be FinSequence of S, x be set holds
  frequency(x,s)=(len s)* FDprobability (x,s)
proof
  let S be finite set, s be FinSequence of S,x be set;
  per cases;
  suppose s is non empty;
    hence thesis by XCMPLX_1:87;
  end;
  suppose s is empty;
    then frequency(x,s)=0;
    hence thesis;
  end;
end;
