Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 5 - Inner Product Spaces - 5.5 Chapter Review - Additional Problems - Page 376: 5

Answer

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Work Step by Step

Determine basic for rowspace $(A)$. $A=\begin{bmatrix} 1 & 3 & 5\\ -1 & -3 & 1\\ 0 & 2 & 3\\ 1& 5 & 2\\ 1 & 5 & 8 \end{bmatrix} \approx \begin{bmatrix} 1 & 3 & 5\\ 0 & 0 & 6\\ 0 & 2 & 3\\ 0& 2 & -3\\ 0 & 2 & 3 \end{bmatrix}\approx \begin{bmatrix} 1 & 3 & 5\\ 0 & 0& 1\\ 0 & 2 & 3\\ 0& 4 & 0\\ 0 & 0 & 0 \end{bmatrix}\approx \begin{bmatrix} 1 & 0 & 0\\ 0 & 0 & 1\\ 0 & 0 & 0\\ 0& 4 & 0\\ 0 & 0 & 0 \end{bmatrix} \approx \begin{bmatrix} 1 & 0 & 0\\ 0 & 0 & 1\\ 0 & 0 & 0\\ 0& 1 & 0\\ 0 & 0 & 0 \end{bmatrix}\approx \begin{bmatrix} 1 & 0 & 0\\ 0 & 1 & 0\\ 0 & 0 & 1\\ 0& 0 & 0\\ 0 & 0 & 0 \end{bmatrix}$ Hence, basic for rowspace $(A):\{(1,0,0),(0,1,0),(0,0,1)\}$ Determine basic for colspace $(A)$. $A=\begin{bmatrix} 1 & 3 & 5\\ -1 & -3 & 1\\ 0 & 2 & 3\\ 1& 5 & 2\\ 1 & 5 & 8 \end{bmatrix} \approx \begin{bmatrix} 1 & 0 & 0\\ -1 & 0 & 6\\ 0 & 2 & 3\\ 1& 2 & -3\\ 1 & 2 & 3 \end{bmatrix}\approx \begin{bmatrix} 1 & 0 & 0\\ -1 & 0& 2\\ 0 & 1 & 1\\ 1 & 1 & -1\\ 1 & 1 & 1 \end{bmatrix}\approx \begin{bmatrix} 1 & 0 & 0\\ -1 & 0 & 2\\ -1 & 1 & 0\\ 0& 1 & -2\\ 0 & 1 & 0 \end{bmatrix} \approx \begin{bmatrix} 1 & 0 & 0\\ -1 & 0 & 1\\ -1 & 1 & 0\\ 0& 1 & -1\\ 0 & 1 & 0 \end{bmatrix}$ Hence, basic for rowspace $(A):\{(1,-1,-1,0,0),(0,0,1,1,1),(0,1,0,-1,0)\}$ Assume $x_1=(1,-1,-1,0,0)\\ x_2=(0,1,2)$ Apply Gram-Schmidt: $v_1=x_1=(1,-1,-1,0,0)\\ v_2=x_2-\frac{}{||v_1||^2}\\ =(0,0,1,1,1)-\frac{}{||(1,-1,-1,0,0)||^2}(1,-1,-1,0,0)\\ =(0,0,1,1,1)-\frac{0.1+0.(-1)+1.(-1)+1.0+1.0}{||1^2+(-1)^2+(-1)^2+0^2+0^2}(1,-1,-1,0,0)\\ =(0,0,1,1,1)+\frac{1}{3}(1,-1,-1,0,0)\\ =\frac{1}{3}(1,-1,2,3,3)\\ w_3=y_3-\frac{}{||w_1||^2}-\frac{}{||w_2||^2}\\ =(0,1,0,-1,0)-\frac{}{||(1,-1,-1,0,0)||^2}(1,-1,-1,0,0)-\frac{}{||\frac{1}{3}(1,-1,2,3,3)||^2}\frac{1}{3}(1,-1,2,3,3)\\ =(0,1,0,-1,0)-\frac{0.1+1.(-1)+0(-1).0+0.0}{1^2+(-1)^2+(-1)^2+0^2+0^2}(1,-1,-1,0,0)-\frac{\frac{1}{3}(0.1+1.(-1)+0.2+(-1).3+0.3)}{\frac{1}{3}.\frac{1}{3}(1^2+(-1)^2+2^2+3^2+3^2)}\frac{1}{3}(1,-1,2,3,3)\\ =(0,1,0,-1,0)+\frac{1}{3}(1,-1,-1,0,0)+\frac{1}{6}(1,-1,2,3,3)\\ =\frac{1}{2}(1,1,0,-1,1)$ To determine an orthogonal set, we obtain: $\frac{w_1}{||w_1||}=\frac{(1,-1,-1,0,0)}{\sqrt 1^2+(-1)^2+(-1)^2+0^2+0^2}=\frac{1}{\sqrt 3}(1,-1,-1,0,0)\\ \frac{w_2}{||w_2||}=\frac{\frac{1}{3}(1,-1,2,3,3)}{\sqrt \frac{1}{3}.\frac{1}{3}.1^2+(-1)^2+2^2+3^2+3^2}=\frac{1}{2\sqrt 6}(1,-1,2,3,3)\\ \frac{w_3}{||w_3||}=\frac{\frac{1}{2}(1,1,0,-1,1)}{\sqrt \frac{1}{2}.\frac{1}{2}.1^2+1^2+0^2+(-1)^2+1^2}=\frac{1}{2}(1,1,0,-1,1)$ The orthogonal basis for colspace $(A)$ is: $\{\frac{1}{\sqrt 3}(1,-1,-1,0,0),\frac{1}{2\sqrt 6}(1,-1,2,3,3),\frac{1}{2}(1,1,0,-1,1)\}$
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