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Using the Integral Test to Estimate Partial Sums of a Series in Calculus

This concept covers the Integral Test for infinite series, applied not only to determine convergence or divergence but to derive explicit bounds on the partial sums of a divergent series in terms of the corresponding improper integral, within single-variable calculus (theory of infinite series). Because the integrand is a decreasing function, comparing left-endpoint and right-endpoint rectangle sums to the area under the curve produces two-sided bounds relating the nth partial sum to the value of the integral evaluated at the same upper limit. This extends the qualitative convergence/divergence conclusion of the Integral Test into a quantitative estimate of the rate of growth (or decay) of partial sums, linking series behavior directly to integral evaluation.