Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 7 - Integration Techniques - 7.4 Trigonometric Substitutions - 7.4 Exercises - Page 538: 65

Answer

$$\frac{{\pi \sqrt 2 }}{{48}}$$

Work Step by Step

$$\eqalign{ & \int_{1/2}^{\left( {\sqrt 2 + 3} \right)/\left( {2\sqrt 2 } \right)} {\frac{{dx}}{{8{x^2} - 8x + 11}}} \cr & \cr & {\text{Factor the denominator}} \cr & = \int_{1/2}^{\left( {\sqrt 2 + 3} \right)/\left( {2\sqrt 2 } \right)} {\frac{{dx}}{{8\left( {{x^2} - x + 11/8} \right)}}} \cr & {\text{Completing the square}} \cr & = \frac{1}{8}\int_{1/2}^{\left( {\sqrt 2 + 3} \right)/\left( {2\sqrt 2 } \right)} {\frac{{dx}}{{{x^2} - x + 1/4 + 9/8}}} \cr & = \frac{1}{8}\int_{1/2}^{\left( {\sqrt 2 + 3} \right)/\left( {2\sqrt 2 } \right)} {\frac{{dx}}{{{{\left( {x - 1/2} \right)}^2} + {{\left( {3/2\sqrt 2 } \right)}^2}}}} \cr & {\text{Let }}u = x - \frac{1}{2},\,\,\,du = dx \cr & {\text{The new limits of integration are:}} \cr & x = \frac{1}{2} \to u = \frac{1}{2} - \frac{1}{2} = 0 \cr & x = \frac{{\sqrt 2 + 3}}{{2\sqrt 2 }} \to u = \frac{{\sqrt 2 + 3}}{{2\sqrt 2 }} - \frac{1}{2} = \frac{{3\sqrt 2 }}{4} \cr & \cr & {\text{Use the change of variable }} \cr & = \frac{1}{8}\int_0^{\frac{{3\sqrt 2 }}{4}} {\frac{{du}}{{{u^2} + {{\left( {3/2\sqrt 2 } \right)}^2}}}} \cr & {\text{Integrate}} \cr & = \frac{1}{8}\left( {\frac{{2\sqrt 2 }}{3}} \right)\left[ {{{\tan }^{ - 1}}\left( {\frac{{2\sqrt 2 u}}{3}} \right)} \right]_0^{\frac{{3\sqrt 2 }}{4}} \cr & = \frac{{\sqrt 2 }}{{12}}\left[ {{{\tan }^{ - 1}}\left( {\frac{{2\sqrt 2 \left( {3\sqrt 2 /4} \right)}}{3}} \right) - 0} \right] \cr & = \frac{{\sqrt 2 }}{{12}}\left[ {{{\tan }^{ - 1}}\left( 1 \right) - 0} \right] \cr & = \frac{{\sqrt 2 }}{{12}}\left( {\frac{\pi }{4}} \right) \cr & = \frac{{\pi \sqrt 2 }}{{48}} \cr} $$
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