If \( \sin \theta=-\frac{2}{3} \), which of the following are possible? Choose all correct answers. \( \sec \theta=\frac{3}{\sqrt{5}} \) and \( \tan \theta=-\frac{2}{\sqrt{5}} \) \( \sec \theta=-\frac{3}{2} \) and \( \tan \theta=\frac{2}{\sqrt{5}} \) \( \cos \theta=-\frac{\sqrt{5}}{3} \) and \( \tan \theta=\frac{2}{\sqrt{5}} \) \( \cos \theta=\frac{\sqrt{5}}{3} \) and \( \tan \theta=\frac{2}{\sqrt{5}} \)
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Bonus Knowledge
To determine the correct statements given \( \sin \theta = -\frac{2}{3} \), we first need to find \( \cos \theta \) using the Pythagorean identity: \[ \sin^2 \theta + \cos^2 \theta = 1 \] Substituting the value of \( \sin \theta \): \[ \left(-\frac{2}{3}\right)^2 + \cos^2 \theta = 1 \implies \frac{4}{9} + \cos^2 \theta = 1 \] This simplifies to: \[ \cos^2 \theta = 1 - \frac{4}{9} = \frac{5}{9} \implies \cos \theta = \pm \frac{\sqrt{5}}{3} \] Now, knowing \( \sin \theta \) is negative, we can determine that \( \theta \) is in either the third or fourth quadrant, where \( \cos \theta \) is positive or negative respectively. This leads us to possible values for \( \tan \theta \): \[ \tan \theta = \frac{\sin \theta}{\cos \theta} \] With \( \sin \theta = -\frac{2}{3} \): 1. If \( \cos \theta = \frac{\sqrt{5}}{3} \), then: \[ \tan \theta = \frac{-\frac{2}{3}}{\frac{\sqrt{5}}{3}} = -\frac{2}{\sqrt{5}} \] 2. If \( \cos \theta = -\frac{\sqrt{5}}{3} \), then: \[ \tan \theta = \frac{-\frac{2}{3}}{-\frac{\sqrt{5}}{3}} = \frac{2}{\sqrt{5}} \] Given this analysis we can evaluate which options can be correct. - First option: \( \sec \theta=\frac{3}{\sqrt{5}} \) does not hold since \( \sec \theta = \frac{1}{\cos \theta} \) and would have no valid \( \cos \theta \) that gives this secant. - Second option: \( \sec \theta=-\frac{3}{2} \) leads to \( \cos \theta = -\frac{2}{3} \), which does not match our derived cosine values. - Third option: \( \cos \theta=-\frac{\sqrt{5}}{3} \) is possible along with \( \tan \theta=\frac{2}{\sqrt{5}} \). - Fourth option: \( \cos \theta=\frac{\sqrt{5}}{3} \) holds with \( \tan \theta=-\frac{2}{\sqrt{5}} \). Thus, the correct answers are: Third option: \( \cos \theta=-\frac{\sqrt{5}}{3} \) and \( \tan \theta=\frac{2}{\sqrt{5}} \) Fourth option: \( \cos \theta=\frac{\sqrt{5}}{3} \) and \( \tan \theta=-\frac{2}{\sqrt{5}} \)