Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 8 - Polar Coordinates; Vectors - Section 8.5 The Dot Product - 8.5 Assess Your Understanding - Page 636: 22

Answer

$\vec v_1=\frac{4}{5}i-\frac{8}{5}j, \vec v_2=\frac{6}{5}i+\frac{3}{5}j$

Work Step by Step

1. Let $\vec v_1=ai+bj, \vec v_2=ci+dj$, we have $a+c=2, b+d=-1$ 2. With $v_1\parallel w$, we have $\frac{b}{a}=\frac{-2}{1}$, thus $2a=-b$ 3. With $v_2\perp w$, we have $c(1)+d(-2)=0$, thus $c=2d$ 4. Combine the above results, we have $-b+4d=4$ and $b+d=-1$, thus $b=-\frac{8}{5}$ and $d=\frac{3}{5}$ 5. Thus the two vectors are $\vec v_1=\frac{4}{5}i-\frac{8}{5}j, \vec v_2=\frac{6}{5}i+\frac{3}{5}j$
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