Linear Algebra: A Modern Introduction

Published by Cengage Learning
ISBN 10: 1285463242
ISBN 13: 978-1-28546-324-7

Chapter 1 - Vectors - 1.2 Length and Angle: The Dot Product - Exercises 1.2 - Page 30: 53


The proof is below.

Work Step by Step

To check the distributive property of a vector: u=$\left[ \begin{array}{ c c } u_{1} \\ u_{2}\\.\\. \\u_{n}\end{array} \right]$ v=$\left[ \begin{array}{ c c } v_{1} \\ v_{2}\\.\\. \\v_{n}\end{array} \right]$ w=$\left[ \begin{array}{ c c } w_{1} \\ w_{2}\\.\\. \\w_{n}\end{array} \right]$ We must show: $u\cdot (v+w)=u\cdot v+u\cdot w$ so $u.(v+w)=\left[ \begin{array}{ c c } u_{1} \\ u_{2}\\.\\. \\u_{n}\end{array} \right].(\left[ \begin{array}{ c c } v_{1} \\ v_{2}\\.\\. \\v_{n}\end{array} \right]+\left[ \begin{array}{ c c } w_{1} \\ w_{2}\\.\\. \\w_{n}\end{array} \right])$ $u\cdot (v+w)=u_{1}(v_{1}+w_{1})+u_{2}(v_{2}+w_{2}).....+u_{n}(v_{n}+w_{n})$ $u\cdot (v+w)=u_{1}v_{1}+u_{1}w_{1}+u_{2}v_{2}+u_{2}w_{2}.......+u_{n}v_{n}+u_{n}w_{n}$ $u\cdot(v+w)=(u_{1}v_{1}+u_{2}v_{2}.....+u_{n}v_{n})+(u_{1}w_{1}+u_{2}w_{2}......+u_{n}w_{n})$ Thus: $u\cdot (v+w)=u\cdot v+u\cdot w$
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