Multivariable Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 0-53849-787-4
ISBN 13: 978-0-53849-787-9

Chapter 12 - Vectors and the Geometry of Space - 12.2 Exercises - Page 823: 28

Answer

$\theta = \tan ^{-1} \frac {3}{4} \approx 36.8 ^{\circ} $

Work Step by Step

The given vector has x-component 8 and y-component 6. Thus, this vector can be drawn as an arrow going from the origin to the point (8, 6). The vector can then be considered the hypotenuse of a right triangle with horizontal leg 8 and vertical leg 6. If we let $\theta $ be the angle between the positive direction of the x-axis and the vector, we can then write: $\tan \theta = \frac {6}{8} = \frac {3}{4} $ To get $\theta$, we use the inverse tangent function: $\theta = \tan ^{-1} \frac {3}{4} \approx 36.8 ^{\circ} $ This answer is correct because the vector is in the first quadrant and so $0 ^{\circ} \lt \theta \lt 90 ^{\circ}$.
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