Linear Algebra and Its Applications (5th Edition)

Published by Pearson
ISBN 10: 032198238X
ISBN 13: 978-0-32198-238-4

Chapter 3 - Determinants - 3.3 Exercises - Page 187: 22

Answer

15 square units

Work Step by Step

We take the parallelogram as ABCD with A=(0,-2), B=(5,-2), C=(-3,1), D=(2,1) We can translate the parallelogram to have one point at the origin (0,0) by subtracting (0,-2) from every point. After doing the subtraction we have ; $\textbf{A=(0,0), B=(5,0), C=(-3,3), D=(2,3)}$ A parallelogram has two vectors with four vertices. The two vectors are $\textbf{u}$ and $\textbf{v}$ $\textbf{u} =AD=\begin{bmatrix}2\\3\end{bmatrix}$ $\textbf{v} =AB=\begin{bmatrix}5\\0\end{bmatrix}$ By forming a matrix $\textbf{Z}$ from the vectors $\textbf{u}$ and $\textbf{v}$ $\textbf{Z} =\left[\textbf{u}, \textbf{v}\right]=\begin{bmatrix}2&5\\3&0\end{bmatrix}$ The area of a parallelogram ABCD is the absolute value of the determinant of $\textbf{Z}$ $Area\,of\,the\,parallelogram=|det\begin{bmatrix}2&5\\3&0\end{bmatrix}|$ $Area\,of\,the\,parallelogram=|det(2\times0-5\times3)|=|-15|=15$ sq units
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