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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 7.AAE.5

Find the limits in Exercises 1–6.
5. lim(n→∞) (1/(n+1) + 1/(n+2) + ... + 1/(2n))

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1
Recognize that the expression is a sum of terms of the form \(\frac{1}{k}\) where \(k\) runs from \(n+1\) to \$2n$. This can be written as \(\sum_{k=n+1}^{2n} \frac{1}{k}\).
Recall that the harmonic series \(H_m = \sum_{k=1}^m \frac{1}{k}\) and use it to rewrite the sum as \(H_{2n} - H_n\).
Use the approximation for large \(n\): \(H_n \approx \ln(n) + \gamma\), where \(\gamma\) is the Euler-Mascheroni constant, to express \(H_{2n} - H_n\) as \(\ln(2n) + \gamma - (\ln(n) + \gamma)\).
Simplify the expression by canceling out \(\gamma\) and combining logarithms: \(\ln(2n) - \ln(n) = \ln\left(\frac{2n}{n}\right) = \ln(2)\).
Conclude that the limit as \(n \to \infty\) of the sum is \(\ln(2)\), since the approximation becomes exact in the limit.

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