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 - 11.4 Cross Products - 11.4 Exercises - Page 797: 30

Answer

\[{\mathbf{u}} \times {\mathbf{v}} = \left\langle { - 2, - 4, - 4} \right\rangle {\text{ and }}{\mathbf{u}} \times {\mathbf{v}} = \left\langle {2,4,4} \right\rangle \]

Work Step by Step

\[\begin{gathered} {\mathbf{u}} = \left\langle { - 4,1,1} \right\rangle ,\,\,\,{\mathbf{v}} = \left\langle {0,1, - 1} \right\rangle \hfill \\ \hfill \\ {\text{Calculate }}{\mathbf{u}} \times {\mathbf{v}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left| {\begin{array}{*{20}{c}} {\mathbf{i}}&{\mathbf{j}}&{\mathbf{k}} \\ { - 4}&1&1 \\ 0&1&{ - 1} \end{array}} \right| \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left| {\begin{array}{*{20}{c}} 1&1 \\ 1&{ - 1} \end{array}} \right|{\mathbf{i}} - \left| {\begin{array}{*{20}{c}} { - 4}&1 \\ 0&{ - 1} \end{array}} \right|{\mathbf{j}} + \left| {\begin{array}{*{20}{c}} { - 4}&1 \\ 0&1 \end{array}} \right|{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left( { - 1 - 1} \right){\mathbf{i}} - \left( {4 - 0} \right){\mathbf{j}} + \left( { - 4 - 0} \right){\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = - 2{\mathbf{i}} - 4{\mathbf{j}} - 4{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left\langle { - 2, - 4, - 4} \right\rangle \hfill \\ \hfill \\ {\text{Calculate }}{\mathbf{v}} \times {\mathbf{u}} \hfill \\ {\mathbf{v}} \times {\mathbf{u}} = \left| {\begin{array}{*{20}{c}} {\mathbf{i}}&{\mathbf{j}}&{\mathbf{k}} \\ 0&1&{ - 1} \\ { - 4}&1&1 \end{array}} \right| \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left| {\begin{array}{*{20}{c}} 1&{ - 1} \\ 1&1 \end{array}} \right|{\mathbf{i}} - \left| {\begin{array}{*{20}{c}} 0&{ - 1} \\ { - 4}&1 \end{array}} \right|{\mathbf{j}} + \left| {\begin{array}{*{20}{c}} 0&1 \\ { - 4}&1 \end{array}} \right|{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left( {1 + 1} \right){\mathbf{i}} - \left( {0 - 4} \right){\mathbf{j}} + \left( {0 + 4} \right){\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = 2{\mathbf{i}} + 4{\mathbf{j}} + 4{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left\langle {2,4,4} \right\rangle \hfill \\ \end{gathered} \]
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