 Use that to approximate a value for formula_34, and then use the recursion relation formula_35 backwards formula_33 times, to unwind it to an approximation for formula_30.Furthermore, this approximation is exact in the limit as formula_33 goes to infinity.Specifically, for a fixed integer formula_39, it is the case that

If formula_39 is not an integer then it is not possible to say whether this equation is true because we have not yet (in this section) defined the factorial function for non-integers.