Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 9 - Section 9.2 - The Dot Product - 9.2 Exercises - Page 646: 27

Answer

comp$_{\vec{v}}$ $\vec{u}=-24$

Work Step by Step

$\vec{u}=7\vec{i}-24\vec{j}$ $,$ $\vec{v}=\vec{j}$ The component of $\vec{u}$ along $\vec{v}$ is comp$_{\vec{v}}$ $\vec{u}=\dfrac{\vec{u}\cdot\vec{v}}{|\vec{v}|}$ where $\vec{u}\cdot\vec{v}$ is the dot product of the vectors $\vec{u}$ and $\vec{v}$ and $|\vec{v}|$ is the magnitude of the vector $\vec{v}$. Find $\vec{u}\cdot\vec{v}$ by multiplying corresponding components and adding: $\vec{u}\cdot\vec{v}=(7)(0)+(-24)(1)=-24$ Find $|\vec{v}|$: $|\vec{v}|=\sqrt{0^{2}+1^{2}}=\sqrt{1}=1$ Substitute $\vec{u}\cdot\vec{v}$ into the formula and evaluate: comp$_{\vec{v}}$ $\vec{u}=\dfrac{-24}{1}=-24$
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