Trigonometry (11th Edition) Clone

Published by Pearson
ISBN 10: 978-0-13-421743-7
ISBN 13: 978-0-13421-743-7

Chapter 6 - Inverse Circular Functions and Trigonometric Equations - Section 6.1 Inverse Circular Functions - 6.1 Exercises - Page 264: 30


The value of $y$ here is $$y=\frac{\pi}{4}$$

Work Step by Step

$$y=\csc^{-1} \sqrt 2$$ First, we see that the domain of inverse cosecant function is $(-\infty,\infty)$. Therefore, in fact when we deal with inverse cosecant function, we do not need to do this checking step. The range of inverse cosecant function is $[-\frac{\pi}{2},0)\hspace{0.2cm}U\hspace{0.2cm}(0,\frac{\pi}{2}]$. In other words, $y\in[-\frac{\pi}{2},0)\hspace{0.2cm}U\hspace{0.2cm}(0,\frac{\pi}{2}]$. We can rewrite $y=\csc^{-1}\sqrt 2$ into $\csc y=\sqrt 2$ We know that $$\csc\frac{\pi}{4}=\frac{1}{\sin\frac{\pi}{4}}=\frac{1}{\frac{\sqrt 2}{2}}=\frac{2}{\sqrt2}=\sqrt 2$$ And $\frac{\pi}{4}$ belongs to the range $[-\frac{\pi}{2},0)\hspace{0.2cm}U\hspace{0.2cm}(0,\frac{\pi}{2}]$. Therefore, the exact value of $y$ here is $$y=\frac{\pi}{4}$$
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