Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 11 - Vectors and Vector-Valued Functions - 11.1 Vectors in the Plane - 11.1 Exercises - Page 768: 46

Answer

$\left(-\dfrac{24\sqrt{61}}{61},-\dfrac{20\sqrt{61}}{61}\right)$ $\left(\dfrac{24\sqrt{61}}{61},\dfrac{20\sqrt{61}}{61}\right)$

Work Step by Step

We are given the points: $P(-4,1)$ $Q(3,-4)$ $R(2,6)$ Find the unit vector $\overrightarrow{u}$ with the same direction as $\overrightarrow{RP}$: $\overrightarrow{u}=\dfrac{\overrightarrow{RP}}{|\overrightarrow{RP}|}=\dfrac{(-4-2,1-6)}{\sqrt{(-4-2)^2+(1-6)^2}}=\dfrac{(-6,-5)}{\sqrt{61}}=\left(-\dfrac{6}{\sqrt{61}},-\dfrac{5}{\sqrt{61}}\right)=\left(-\dfrac{6\sqrt{61}}{61},-\dfrac{5\sqrt{61}}{61}\right)$ Two unit vectors parallel to $\overrightarrow{RP}$ are: $4\overrightarrow{u}=4\left(-\dfrac{6\sqrt{61}}{61},-\dfrac{5\sqrt{61}}{61}\right)=\left(-\dfrac{24\sqrt{61}}{61},-\dfrac{20\sqrt{61}}{61}\right)$ $-4\overrightarrow{u}=-4\left(-\dfrac{6\sqrt{61}}{61},-\dfrac{5\sqrt{61}}{61}\right)=\left(\dfrac{24\sqrt{61}}{61},\dfrac{20\sqrt{61}}{61}\right)$
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