Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 7 - Section 7.5 - Vectors: An Algebraic Approach - 7.5 Problem Set - Page 405: 57

Answer

\[ 2=|W|, 240^{\circ}=\theta \]

Work Step by Step

Given \[ -i-\sqrt{3} j=W \] Here the $x$ component of the vector is $-1=W_{x}$, and the $y$ component of the vector is $-\sqrt{3}=W_{y}$ The magnitude of the vector W is \[ |\sqrt{W_{x}^{2}+W_{y}^{2}}=W| \] Substitute $W_{x}$ and $W_{y}$ values \[ \begin{aligned} &\sqrt{(-1)^{2}+(-\sqrt{3})^{2}}=|W| \\ &=\sqrt{3+1} \\ &=\sqrt{4} \\ &=2 \end{aligned} \] $\theta$ is the angle made with the positive $x-$ axis and the vector. \[ \frac{W_{x}}{W_{y}}=\tan \theta \] \[ \begin{aligned} &=\frac{-\sqrt{3}}{-1} \\ \tan \theta &=\sqrt{3} \\ \theta &=\tan ^{-1} \sqrt{3} \\ &=240^{\circ} \end{aligned} \] The angle is $240^{\circ}$ but not $60^{\circ}$ because the $x$ component and $y$ component of the given vector are negative. Thus the angle must be in Quadrant III.
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