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: 31

Answer

\[{\mathbf{u}} \times {\mathbf{v}} = \left\langle {6,11,5} \right\rangle {\text{ and }}{\mathbf{u}} \times {\mathbf{v}} = \left\langle { - 6, - 11, - 5} \right\rangle \]

Work Step by Step

\[\begin{gathered} {\mathbf{u}} = \left\langle {2,3, - 9} \right\rangle ,\,\,\,{\mathbf{v}} = \left\langle { - 1,1, - 1} \right\rangle \hfill \\ \hfill \\ {\text{Calculate }}{\mathbf{u}} \times {\mathbf{v}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left| {\begin{array}{*{20}{c}} {\mathbf{i}}&{\mathbf{j}}&{\mathbf{k}} \\ 2&3&{ - 9} \\ { - 1}&1&{ - 1} \end{array}} \right| \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left| {\begin{array}{*{20}{c}} 3&{ - 9} \\ 1&{ - 1} \end{array}} \right|{\mathbf{i}} - \left| {\begin{array}{*{20}{c}} 2&{ - 9} \\ { - 1}&{ - 1} \end{array}} \right|{\mathbf{j}} + \left| {\begin{array}{*{20}{c}} 2&3 \\ { - 1}&1 \end{array}} \right|{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left( { - 3 + 9} \right){\mathbf{i}} - \left( { - 2 - 9} \right){\mathbf{j}} + \left( {2 + 3} \right){\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = 6{\mathbf{i}} + 11{\mathbf{j}} + 5{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left\langle {6,11,5} \right\rangle \hfill \\ \hfill \\ {\text{Calculate }}{\mathbf{v}} \times {\mathbf{u}} \hfill \\ {\mathbf{v}} \times {\mathbf{u}} = \left| {\begin{array}{*{20}{c}} {\mathbf{i}}&{\mathbf{j}}&{\mathbf{k}} \\ { - 1}&1&{ - 1} \\ 2&3&{ - 9} \end{array}} \right| \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left| {\begin{array}{*{20}{c}} 1&{ - 1} \\ 3&{ - 9} \end{array}} \right|{\mathbf{i}} - \left| {\begin{array}{*{20}{c}} { - 1}&{ - 1} \\ 2&{ - 9} \end{array}} \right|{\mathbf{j}} + \left| {\begin{array}{*{20}{c}} { - 1}&1 \\ 2&3 \end{array}} \right|{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left( { - 9 + 3} \right){\mathbf{i}} - \left( {9 + 2} \right){\mathbf{j}} + \left( { - 3 - 2} \right){\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = - 6{\mathbf{i}} - 11{\mathbf{j}} - 5{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left\langle { - 6, - 11, - 5} \right\rangle \hfill \\ \end{gathered} \]
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