Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 7: Transcendental Functions - Practice Exercises - Page 439: 47

Answer

$$ - \cot \left( {1 + \ln r} \right) + C $$

Work Step by Step

$$\eqalign{ & \int {\frac{1}{r}{{\csc }^2}\left( {1 + \ln r} \right)} dr \cr & {\text{integrate by the substitution method}} \cr & {\text{set }}u = \ln r{\text{ then }}\frac{{du}}{{dr}} = \frac{1}{r},\,\,\,\,dr = rdu \cr & {\text{write the integrand in terms of }}u \cr & \int {\frac{1}{r}{{\csc }^2}\left( {1 + \ln r} \right)} dr = \int {\frac{1}{r}{{\csc }^2}u} \left( {rdu} \right) \cr & {\text{cancel common term }}r \cr & = \int {{{\csc }^2}u} du \cr & {\text{integrating}}{\text{,}} \cr & = - \cot u + C \cr & {\text{replace }}\left( {1 + \ln r} \right){\text{ for }}u \cr & = - \cot \left( {1 + \ln r} \right) + C \cr} $$
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