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: 58

Answer

\[ 150^{\circ}=\theta, 4=|W| \]

Work Step by Step

Given \[ -2 \sqrt{3} i+2 j=F \] The magnitude of the vector $\mathrm{W}$ is \[ \sqrt{F_{x}^{2}+F_{y}^{2}}=|F| \] Replace $F_{x}$ with $F_{y}$ values \[ \begin{aligned} &\sqrt{(2)^{2}+(-2 \sqrt{3})^{2}}=|F| \\ &=\sqrt{4+4 \cdot 3} \\ &=\sqrt{16} \\ &=4 \end{aligned} \] $\theta$ is the angle made with the positive $x-$axis, the vector. \[ \begin{aligned} &\frac{F_{x}}{F_{y}}=\tan \theta \\ &=\frac{2}{-2 \sqrt{3}} \\ &-\frac{1}{\sqrt{3}}=\tan \theta \\ &\tan ^{-1}\left(\frac{-1}{\sqrt{3}}\right)=\theta \\ &=150^{\circ} \end{aligned} \] The angle is $150^{\circ}$ but not $330^{\circ}$ because the $x$ component is negative, and the $y$ component is positive. Thus the angle must be in Quadrant II.
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