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: 21

Answer

$$11$$

Work Step by Step

\[\begin{gathered} {\mathbf{u}} = 3{\mathbf{i}} - {\mathbf{j}},\,\,\,{\mathbf{v}} = 3{\mathbf{j}} + 2{\mathbf{k}} \hfill \\ {\text{The area of the parallelogram is given by }}\left| {{\mathbf{u}} \times {\mathbf{v}}} \right| \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left| {\begin{array}{*{20}{c}} {\mathbf{i}}&{\mathbf{j}}&{\mathbf{k}} \\ 3&{ - 1}&0 \\ 0&3&2 \end{array}} \right| \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left| {\begin{array}{*{20}{c}} { - 1}&0 \\ 3&2 \end{array}} \right|{\mathbf{i}} - \left| {\begin{array}{*{20}{c}} 3&0 \\ 0&2 \end{array}} \right|{\mathbf{j}} + \left| {\begin{array}{*{20}{c}} 3&{ - 1} \\ 0&3 \end{array}} \right|{\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = \left( { - 2 - 0} \right){\mathbf{i}} - \left( {6 - 0} \right){\mathbf{j}} + \left( {9 - 0} \right){\mathbf{k}} \hfill \\ {\mathbf{u}} \times {\mathbf{v}} = - 2{\mathbf{i}} - 6{\mathbf{j}} + 9{\mathbf{k}} \hfill \\ {\text{Area}} = \left| {{\mathbf{u}} \times {\mathbf{v}}} \right| \hfill \\ {\text{Area}} = \left| { - 2{\mathbf{i}} - 6{\mathbf{j}} + 9{\mathbf{k}}} \right| \hfill \\ {\text{Area}} = \sqrt {{{\left( { - 2} \right)}^2} + {{\left( { - 6} \right)}^2} + {{\left( 9 \right)}^2}} \hfill \\ {\text{Area}} = \sqrt {121} \hfill \\ {\text{Area}} = 11 \hfill \\ \end{gathered} \]
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