Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 8 - Techniques of Integration - 8.9 Numerical Integration - Exercises - Page 457: 10

Answer

$$M_{5}=1.117,\ \ \ T_{5}=1.120$$

Work Step by Step

Given $$\int_{2}^{3} \frac{1}{\ln x} d x ,\ \ \ \ N=5$$ Since $\Delta x=\dfrac{b-a}{n}=\dfrac{1}{5}=0.2$ Therefore, the sub intervals consist of $$[2,2.2],[2.2,2.4],[2.4,2.6],[2.6,2.8],[2.8,3] $$ The midpoints of these sub intervals are $$\{ 2.1, 2.3,2.5,2.7,2.9\}$$ Hence \begin{align*} M_{n}&= \sum_{i=1}^{n}f(m_i)\Delta x\\ M_{5}&= \left[ f(m_1)+ f(m_2)+ ..............+f(m_4)\right]\Delta x\\ &=\frac{1}{2}\left[ f(2.1)+ f(2.3)+ f(2.5)+ f(2.7)+ f(2.9)\right]\\ &\approx 1.117 \end{align*} Now find $T_5$ \begin{align*} T_{n}&=\dfrac{1}{2}\left[f(x_0)+2f(x_1)+2f(x_2)+.....+2f(x_{n-1})+f(x_n)\right]\Delta x\\ T_{5}&=\dfrac{1}{2}\left[f(x_0)+2f(x_1)+2f(x_2)+2f(x_{3})+2f(x_4)+f(x_5)\right]\Delta x\\ &=\dfrac{1}{10}\left[f(2)+2f(2.2)+2f(2.4)+2f(2.6)+2f(2.8)+f(3)\right] \\ &\approx 1.120 \end{align*}
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