theorem
  for p being XFinSequence, x being object holds last(p^<%x%>) = x
proof
  let p be XFinSequence, x be object;
  dom(p^<%x%>) = len(p^<%x%>)
    .= len p + 1 by Th72
    .= len p +^ 1 by CARD_2:36
    .= succ len p by ORDINAL2:31;
  hence last(p^<%x%>) = (p^<%x%>).len p by ORDINAL2:6
    .= x by Th33;
end;
