Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 1 - Section 1.3 - Definition I: Trigonometric Functions - 1.3 Problem Set - Page 33: 60

Answer

$\sin{\theta} =\dfrac{\sqrt{2}}{2}$ $\cos{\theta} =\dfrac{\sqrt{2}}{2}$ $\tan{\theta} = 1$ $\csc{\theta} =\sqrt{2}$ $\sec{\theta} =\sqrt{2}$ $\cot{\theta} =1$

Work Step by Step

$\because \cos{\theta} = \dfrac{x}{r} = \dfrac{\sqrt{2}}{2}$ $\therefore x = \sqrt{2} \hspace{10pt} \& \hspace{10pt} r = 2$ $$r^2 = x^2+y^2 \\ y^2 = r^2-x^2 \\ y = \pm \sqrt{r^2-x^2} =\pm \sqrt{2^2-(\sqrt{2})^2} = \pm \sqrt{2}$$ As $\theta$ terminates in $QI$, any point on its terminal side will have a positive $y$ coordinate. $\therefore y = \sqrt{2}$ $\sin{\theta} = \dfrac{y}{r} = \dfrac{\sqrt{2}}{2}$ $\tan{\theta} = \dfrac{y}{x} = \dfrac{\sqrt{2}}{\sqrt{2}} = 1$ $\csc{\theta} = \dfrac{1}{\sin{\theta}} = \sqrt{2}$ $\sec{\theta} = \dfrac{1}{\cos{\theta}} = \sqrt{2}$ $\cot{\theta} = \dfrac{1}{\tan{\theta}} = 1$
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