MathDB
Miklós Schweitzer 1960- Problem 8

Source:

November 21, 2015
college contests

Problem Statement

8. Let ff be a bounded real function defined on the unit cube HH of the nn-dimensional space and, for a given yy, let AyA_y and ByB_y denote the parts of the interior of HH on which f>yf>y and f<yf<y, respectively. Show that ff is integrable in the Riemannian sense if and only if for every yy almost all points of AyA_y and ByB_y are inner points. (R. 9)