Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 7 - Techniques of Integration - Review - Exercises - Page 578: 40

Answer

\[3^{\frac{1}{4}}-1\]

Work Step by Step

Let \[I=\int_{\frac{π}{4}}^{\frac{π}{3}}\frac{\sqrt{\tan\theta}}{\sin 2\theta}\;d\theta\;\;\;\;\ldots (1)\] Consider \[I_1=\int\frac{\sqrt{\tan\theta}}{\sin 2\theta}\;d\theta\] \[I_1=\int\frac{\sqrt{ \frac{\sin\theta}{\cos\theta} }}{2\sin \theta\cos\theta}\;d\theta\] \[I_1=\int\frac{1}{2\sin^{\frac{1}{2}}\theta\cos^{\frac{3}{2}}\theta}\;d\theta\] \[I_1=\int\frac{\sec^2\theta}{2\sqrt{\tan\theta}}\;d\theta\] Substitute $\;t=\tan\theta$ \[\Rightarrow dt=\sec^2\theta d\theta\] \[I_1=\int\frac{dt}{2\sqrt{t}}=\frac{1}{2}\int t^{-\frac{1}{2}}dt\] \[I_1=\frac{1}{2}(2\sqrt{t})=\sqrt t\] \[I_1=\sqrt{\tan\theta}+C\;\;\;\ldots (2)\] Where $C$ is constant of integration Using (2) in (1) \[I=\left[\sqrt{\tan\theta}\right]_{\frac{π}{4}}^{\frac{π}{3}}\] \[I=\sqrt{\tan \frac{π}{3} }-\sqrt{\tan \frac{π}{4} }\] \[I=\sqrt{\sqrt{3}}-1\] \[I=3^{\frac{1}{4}}-1\] Hence \[I=3^{\frac{1}{4}}-1\;\;.\]
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