Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 16 - Multiple Integration - 16.6 Change of Variables - Exercises - Page 905: 27

Answer

Please see the figure attached. The translate of the linear mapping is $G\left( {u,v} \right) = \left( {1 + 2u + v,1 + 5u + 3v} \right)$

Work Step by Step

We sketch the parallelogram ${\cal P}$ in $xy$-plane with vertices $\left( {1,1} \right)$, $\left( {2,4} \right)$, $\left( {3,6} \right)$, $\left( {4,9} \right)$. From the figure attached we see that ${\cal P}$ is translated by $\left( {1,1} \right)$ from the origin. So, $a=1$, $b=1$. The translate of a linear mapping has the form: $G\left( {u,v} \right) = \left( {a + Au + Cv,b + Bu + Dv} \right)$ Substituting $a=1$ and $b=1$ in $G$ we get $G\left( {u,v} \right) = \left( {1 + Au + Cv,1 + Bu + Dv} \right)$ The domain ${{\cal R}_0} = \left[ {0,1} \right] \times \left[ {0,1} \right]$ has vertices $\left( {0,0} \right)$, $\left( {0,1} \right)$, $\left( {1,1} \right)$, $\left( {1,0} \right)$. Notice that ${\cal R}$ is spanned by $\left( {1,0} \right)$ and $\left( {0,1} \right)$ and ${\cal P}$ is spanned by $\left( {3,6} \right)$ and $\left( {2,4} \right)$. Substituting these vertices in $G$ and equate each with the corresponding vertex in the $xy$-plane, we get $G\left( {0,0} \right) = \left( {1,1} \right)$ $G\left( {0,1} \right) = \left( {1 + C,1 + D} \right) = \left( {2,4} \right)$ $G\left( {1,1} \right) = \left( {1 + A + C,1 + B + D} \right) = \left( {4,9} \right)$ $G\left( {1,0} \right) = \left( {1 + A,1 + B} \right) = \left( {3,6} \right)$ From these results, we obtain $A=2$, $B=5$, $C=1$, $D=3$. Therefore, the translate of the linear mapping is $G\left( {u,v} \right) = \left( {1 + 2u + v,1 + 5u + 3v} \right)$
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