See attached this lemma 3 and the last part of the proof above lemma 3, which is the inequality 'which suffices for this claim' which then proceeds to lemma 3; in this inequality methods, where one shows that both the rhs and lhs approximately equal each other, that the middle term must also, have a name; some kind of mean approximation theorem; intermediate asymptotic value theorem?
If one can partition a countably infinite sequence,A of numbers into two (countably infinite) sub-sequences B1, B2 such A =B1\cupB2;and the limiting relative frequency(a \in B1) = x, & the limiting relative frequency ( a\in B2 )=y s.t y>x;when can one can say that the limiting relative frequency(a\in A) is defined, such that it is bounded above by y and below by x,
so that one can say limrelfreq(a\inB1)