Thomas' Calculus 13th Edition

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

Chapter 5: Integrals - Section 5.5 - Indefinite Integrals and the Substitution Method - Exercises 5.5 - Page 295: 36

Answer

$$ - 2\csc \sqrt \theta + C$$

Work Step by Step

$$\eqalign{ & \int {\frac{{\cos \sqrt \theta }}{{\sqrt \theta {{\sin }^2}\sqrt \theta }}} d\theta \cr & = \int {\frac{{\cos \sqrt \theta }}{{\sqrt \theta {{\left( {\sin \sqrt \theta } \right)}^2}}}} d\theta \cr & \cr & {\text{Integrate by the substitution method}} \cr & u = \sin \sqrt \theta ,\,\,\,\,\,du = \cos \sqrt \theta \left( {\frac{1}{{2\sqrt \theta }}} \right)d\theta ,\,\,\,\,\,\,d\theta = \left( {\frac{{2\sqrt \theta }}{{\cos \sqrt \theta }}} \right)du \cr & {\text{Write the integrand in terms of }}u \cr & \int {\frac{{\cos \sqrt \theta }}{{\sqrt \theta {{\left( {\sin \sqrt \theta } \right)}^2}}}} d\theta = \int {\frac{{\cos \sqrt \theta }}{{\sqrt \theta {{\left( u \right)}^2}}}} \left( {\frac{{2\sqrt \theta }}{{\cos \sqrt \theta }}} \right)du \cr & {\text{Simplifying}} \cr & = \int {\frac{2}{{{u^2}}}du} \cr & = - \frac{2}{u} + C \cr & \cr & {\text{Write in terms of }}\theta;{\text{ substitute }}\sin \sqrt \theta {\text{ for }}u \cr & = - \frac{2}{{\sin \sqrt \theta }} + C \cr & = - 2\csc \sqrt \theta + C \cr} $$
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