Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 5 - Section 5.1 - The Unit Circle - 5.1 Exercises - Page 408: 54

Answer

(a) Reference Number: $\pi/4$ (b) Terminal Point: $(\sqrt 2/ 2, -\sqrt 2/2)$

Work Step by Step

1. Find an angle that has the same terminal point as $-41\pi/4$, and is between 0 and 2$\pi$. $$-\frac{41\pi}{4} + 6(2\pi) = -\frac{41\pi}{4} + \frac{48\pi}{4} = \frac{7\pi}{4}$$ 2. $7\pi/4$ is in Quadrant IV, thus, the Reference Number is given by the equation: $$t^- = 2\pi - \frac{7\pi}{4} = \frac{8\pi}{4} - \frac{7\pi}{4} = \frac{\pi} 4$$ 3. According to the Table 1, the terminal point for $\pi/4$ is $(\sqrt 2/2, \sqrt 2/2)$. In Quadrant IV: x-coordinate is positive and y-coordinate is negative. Therefore, the terminal point is: $(\sqrt 2/ 2, -\sqrt 2/2)$
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