Let it be supposed there is a function f: D → R where D, R &sube R and that there is a closed interval I = [a,b] such that I &sube D. If we have a finite set of points {x0, x1, x2, ... xn} such that a = x0 < x1 < x2 ... < xn = b, then this set creates a partition P = {[x0, x1), [x1, x2), ... [xn-1, xn]} of I.
If is a partition with elements of , then the Riemann sum of over with the partition is defined as
Suppose we have
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