f(x) on an interval [a, b] with respect to partitions into subintervals that do
not necessarily have equal length. Moreover, for every € > 0 there exists
δ >0 such that the Riemann integral of f over [a, b] is estimated to within
e by the Riemann sum of any partition whose (possibly varying) lengths of
subintervals are all < δ. Work through the following example.
Fig: 1
Fig: 2