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 - Chapter Test - Page 656: 16

Answer

$\dfrac{ \sqrt 2}{2}i -\dfrac{\sqrt 2}{2}j$

Work Step by Step

If a vector $v$ initiates at point $A(x_1,y_1)$ and terminates at $B(x_2,y_2)$, then $v =\lt x_2-x_1, y_2-y_1 \gt =(x_2-x_1)i+(y_2-y_1) \ j$ Here, we have: $A=(3\sqrt 2, 7 \sqrt 2)$ and $B=(8\sqrt 2, 2 \sqrt 2)$ Therefore, $v=(8\sqrt 2-3 \sqrt 2)i+(2\sqrt 2-7 \sqrt 2) \ j \\= 5 \sqrt 2i -5 \sqrt 2 \ j$ The magnitude of a vector can be determined using the formula $||v||=\sqrt{p^2+q^2} (1)$ We will use the formula (1) to obtain: $||v||=\sqrt{(5\sqrt 2)^2+(-5 \sqrt 2)^2}\\ =\sqrt{50+50}\\ =\sqrt{100}\\=10$ The unit vector $u$ in the same direction as $v$ is given by: $u=\dfrac{v}{||v||}$ $u=\dfrac{v}{||v||}=\dfrac{5 \sqrt 2i -5 \sqrt 2 \ j}{10}=\dfrac{ \sqrt 2}{2}i -\dfrac{\sqrt 2}{2}j$
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