|S(a,M 1)f(x)dx-S(a,M2)f(x)dx|=|S(M 1,M2)f(x)dx | & lt; The fifth letter of the Greek alphabet.
Then S(a, oo)f(x)dx converges. Where S(a, oo) represents a generalized integral from a to infinity.
2) Point set A is understood as several sets (the size of elements can be compared). If there is a real number m, let
X & gt=m, and x belongs to A (1).
Then m is called the lower bound of a, and the maximum m that satisfies (1) is called the lower supremum of a.
3) Any sequence can choose a convergent subsequence. In all the convergent subsequences of sequence ak, the maximum limit is called the upper limit of sequence ak.