Published online by Cambridge University Press: 24 October 2008
Hobson has given a proof of this theorem in its fullest generality. The present note gives an alternative for part of Hobson's argument. The theorem may be stated in two forms. If f(x) is a function of x, monotone when a ≤ x ≤ b, and φ(x) is integrable over the same range, then
where a ≤ X ≤ b,
(ii) the same holds with a < X < b except in some trivial cases where f(x) is constant in the open interval a < x < b. The form (ii) is not mentioned by Hobson.
* Proc. Lond. Math. Soc., Ser. 2, Vol. VII, pp. 14–23 (1909).Google Scholar
* For the method of proof of this theorem, see Phil. Trans. Roy. Soc. A, 211, pp. 413–416 (1911).Google Scholar