Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 4 - Graphs of the Circular Functions - Section 4.4 Graphs of the Secant and Cosecant Functions - 4.4 Exercises - Page 174: 3

Answer

$D$

Work Step by Step

The secant function is undefined when $x=-\frac{\pi}{2}, \frac{\pi}{2}, \frac{3\pi}{2}, ...$ Thus, its graph has the vertical asymptotes $x=-\frac{\pi}{2}, \frac{\pi}{2}, \frac{3\pi}{2},...$. RECALL: The graph of the function $y=\sec{(x-d)}$ involves a phase (horizontal) shift of the parent function $y=\sec{x}$. The shift is to the right when $d\gt0$ and to the left when $d\lt0$. The given function has $d=\frac{\pi}{2}$ so it involves a phase shift of $\frac{\pi}{2}$ to the right. Thus, its vertical asymptotes are $x=0, \pi, 2\pi, ...$ The only possible graph among the choices are the ones in Options B and D. Note that when $x=\frac{\pi}{2}$ , the value of $y=\sec{(x-\frac{\pi}{2})}$ is $1$. Only the graph in Option $C$ satisfies this. Thus, the graph of $y=\sec{(x-\frac{\pi}{2})}$ must be the one in Option $D$.
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