Calculus: Early Transcendentals (2nd Edition)

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

Chapter 11 - Vectors and Vector-Valued Functions - 11.6 Calculus of Vector-Valued Functions - 11.6 Exercises - Page 815: 38

Answer

\[\left( {8{t^3} - 4t} \right){\mathbf{i}} - \left( { - 6{t^5} + 2} \right){\mathbf{j}} + \left( { - 5{t^4} + 4{t^3}} \right){\mathbf{k}}\]

Work Step by Step

\[\begin{gathered} \frac{d}{{dt}}\left( {\left( {{t^3}{\mathbf{i}} - 2t{\mathbf{j}} - 2{\mathbf{k}}} \right) \times \left( {t{\mathbf{i}} - {t^2}{\mathbf{j}} - {t^3}{\mathbf{k}}} \right)} \right) \hfill \\ \hfill \\ \left( {{t^3}{\mathbf{i}} - 2t{\mathbf{j}} - 2{\mathbf{k}}} \right) \times \left( {t{\mathbf{i}} - {t^2}{\mathbf{j}} - {t^3}{\mathbf{k}}} \right) \hfill \\ = \left| {\begin{array}{*{20}{c}} {\mathbf{i}}&{\mathbf{j}}&{\mathbf{k}} \\ {{t^3}}&{ - 2t}&{ - 2} \\ t&{ - {t^2}}&{ - {t^3}} \end{array}} \right| = \left| {\begin{array}{*{20}{c}} { - 2t}&{ - 2} \\ { - {t^2}}&{ - {t^3}} \end{array}} \right|{\mathbf{i}} - \left| {\begin{array}{*{20}{c}} {{t^3}}&{ - 2} \\ t&{ - {t^3}} \end{array}} \right|{\mathbf{j}} + \left| {\begin{array}{*{20}{c}} {{t^3}}&{ - 2t} \\ t&{ - {t^2}} \end{array}} \right|{\mathbf{k}} \hfill \\ = \left( {2{t^4} - 2{t^2}} \right){\mathbf{i}} - \left( { - {t^6} + 2t} \right){\mathbf{j}} + \left( { - {t^5} + 2{t^2}} \right){\mathbf{k}} \hfill \\ \hfill \\ {\text{Calculate the derivative}} \hfill \\ = \left( {8{t^3} - 4t} \right){\mathbf{i}} - \left( { - 6{t^5} + 2} \right){\mathbf{j}} + \left( { - 5{t^4} + 4{t^3}} \right){\mathbf{k}} \hfill \\ \end{gathered} \]
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