Trigonometry (10th Edition)

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

Chapter 6 - Review Exercises - Page 285: 46

Answer

$\color{blue}{\left\{45^o, 153.4^o, 225^o, 333.4^o\right\}}$

Work Step by Step

Let $u=\tan{\theta}$ Replacing $\tan{\theta}$ with $u$ gives: $2u^2=u+1 \\2u^2-u-1=0$ Factor the trinomial to obtain: $(2u+1)(u-1)=0$ Use the Zero Factor Property by equating each factor to zero, then solve each equation to obtain: \begin{array}{ccc} &2u+1=0 &\text{or} &u-1=0 \\&2u=-1 &\text{or} &u=1 \\&u=-\frac{1}{2} &\text{or} &u=1 \end{array} Replace $u$ with $\tan{\theta}$ to obtain: \begin{array}{ccc} &\tan{\theta}=-\frac{1}{2} &\text{or} &\tan{\theta}=1 \\&\theta=\tan^{-1}{(-\frac{1}{2})} &\text{or} &\theta=\tan^{-1}{(1)} \end{array} Use the inverse tangent function of a calculator to obtain: $\theta=-26.56505118^o\approx 26.6^o \text{ or } \theta=45^o$ Since the period of the tangent function is $180^o$, then the following are also solutions of the given equation: $-26.6^o+180^o=153.4^o \\153.4^o+180^o=333.4^o$ and $45^o+180^o=225^o$ Note that $-26.6^o$ is not within the interval $[0^o, 360^o)$. Therefore, the solutions to the given equation are $\color{blue}{45^o, 153.4^o, 225^o, \text{ and }333.4^o}$.
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