Thomas' Calculus 13th Edition

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

Chapter 8: Techniques of Integration - Section 8.2 - Integration by Parts - Exercises 8.2 - Page 455: 50

Answer

$$\frac{\pi }{{12}} + \frac{{\sqrt 3 }}{2} - 1$$

Work Step by Step

$$\eqalign{ & \int_0^{1/\sqrt 2 } {2x{{\sin }^{ - 1}}\left( {{x^2}} \right)} dx \cr & {\text{Using the integration by parts method }} \cr & \,\,\,\,\,{\text{Let }}\,\,\,\,\,u = {\sin ^{ - 1}}\left( {{x^2}} \right),\,\,\,\,du = \frac{{2x}}{{\sqrt {1 - {{\left( {{x^2}} \right)}^2}} }}\,\,\,dx \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,dv = 2xdx,\,\,\,\,v = {x^2} \cr & \cr & {\text{Integration by parts formula }}\int {udv} = uv - \int {vdu.{\text{ T}}} {\text{hen}}{\text{,}} \cr & \int {2x{{\sin }^{ - 1}}\left( {{x^2}} \right)} dx = {x^2}{\sin ^{ - 1}}\left( {{x^2}} \right) - \int {{x^2}} \frac{{2x}}{{\sqrt {1 - {{\left( {{x^2}} \right)}^2}} }}\,\,\,dx \cr & \int {2x{{\sin }^{ - 1}}\left( {{x^2}} \right)} dx = {x^2}{\sin ^{ - 1}}\left( {{x^2}} \right) - \int {\frac{{2{x^3}}}{{\sqrt {1 - {x^4}} }}} \,dx \cr & \int {2x{{\sin }^{ - 1}}\left( {{x^2}} \right)} dx = {x^2}{\sin ^{ - 1}}\left( {{x^2}} \right) + \frac{1}{2}\int {{{\left( {1 - {x^4}} \right)}^{ - 1/2}}\left( { - 4{x^3}} \right)} \,dx \cr & {\text{using the power rule for integration}} \cr & = {x^2}{\sin ^{ - 1}}\left( {{x^2}} \right) + \frac{1}{2}\left( {\frac{{{{\left( {1 - {x^4}} \right)}^{1/2}}}}{{1/2}}} \right) + C \cr & = {x^2}{\sin ^{ - 1}}\left( {{x^2}} \right) + \sqrt {1 - {x^4}} + C \cr & \cr & \int_0^{1/\sqrt 2 } {2x{{\sin }^{ - 1}}\left( {{x^2}} \right)} dx = \left( {{x^2}{{\sin }^{ - 1}}\left( {{x^2}} \right) + \sqrt {1 - {x^4}} } \right)_0^{1/\sqrt 2 } \cr & {\text{Evaluating}} \cr & = \left( {{{\left( {\frac{1}{{\sqrt 2 }}} \right)}^2}{{\sin }^{ - 1}}\left( {{{\left( {\frac{1}{{\sqrt 2 }}} \right)}^2}} \right) + \sqrt {1 - {{\left( {\frac{1}{{\sqrt 2 }}} \right)}^4}} } \right) - \left( {{{\left( 0 \right)}^2}{{\sin }^{ - 1}}\left( {{{\left( 0 \right)}^2}} \right) + \sqrt {1 - {{\left( 0 \right)}^4}} } \right) \cr & = \left( {\frac{1}{2}{{\sin }^{ - 1}}\left( {\frac{1}{2}} \right) + \sqrt {1 - \frac{1}{4}} } \right) - \left( 1 \right) \cr & = \frac{1}{2}\left( {\frac{\pi }{6}} \right) + \sqrt {\frac{3}{4}} - 1 \cr & = \frac{\pi }{{12}} + \frac{{\sqrt 3 }}{2} - 1 \cr} $$
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