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If angle \( \theta \) lies in Quadrant II and \( \sin \theta=\frac{3}{\sqrt{45}} \). Determine possible coordinates for point P on the terminal arm of angle \( \theta \).

Ask by Mckenzie Welch. in Canada
Jan 28,2025

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Tutor-Verified Answer

Answer

The coordinates of point \( P \) are \( (-6, 3) \).

Solution

Given that angle \( \theta \) lies in Quadrant II and \( \sin \theta = \frac{3}{\sqrt{45}} \), we can determine the coordinates of a point \( P(x, y) \) on the terminal arm of \( \theta \). 1. **Simplify \( \sin \theta \):** \[ \sin \theta = \frac{3}{\sqrt{45}} = \frac{3}{3\sqrt{5}} = \frac{1}{\sqrt{5}} \] 2. **Using the Pythagorean identity:** \[ \sin^2 \theta + \cos^2 \theta = 1 \\ \left(\frac{1}{\sqrt{5}}\right)^2 + \cos^2 \theta = 1 \\ \frac{1}{5} + \cos^2 \theta = 1 \\ \cos^2 \theta = \frac{4}{5} \\ \cos \theta = \pm \frac{2}{\sqrt{5}} \] Since \( \theta \) is in Quadrant II, \( \cos \theta \) is negative: \[ \cos \theta = -\frac{2}{\sqrt{5}} \] 3. **Determine the coordinates \( (x, y) \):** - Let the hypotenuse (radius) \( r = \sqrt{45} \). - \( y = r \sin \theta = \sqrt{45} \times \frac{1}{\sqrt{5}} = \frac{3\sqrt{5}}{\sqrt{5}} = 3 \) - \( x = r \cos \theta = \sqrt{45} \times \left( -\frac{2}{\sqrt{5}} \right) = -\frac{6\sqrt{5}}{\sqrt{5}} = -6 \) Therefore, the coordinates of point \( P \) on the terminal arm of angle \( \theta \) are: \[ \boxed{\,(-6,\ 3)\,} \]

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Bonus Knowledge

To find the coordinates of point P on the terminal arm of angle \( \theta \), we first need to simplify the sine value. Given \( \sin \theta = \frac{3}{\sqrt{45}} \), we can simplify \( \sqrt{45} \) to \( 3\sqrt{5} \). Thus, \( \sin \theta = \frac{3}{3\sqrt{5}} = \frac{1}{\sqrt{5}} \). Since \( \sin \theta \) represents the y-coordinate in the unit circle, we have \( y = \frac{1}{\sqrt{5}} \). Now, in Quadrant II, the x-coordinate will be negative. To find the x-coordinate, we can use the Pythagorean identity \( \sin^2 \theta + \cos^2 \theta = 1 \): \[ \left(\frac{1}{\sqrt{5}}\right)^2 + \cos^2 \theta = 1 \implies \frac{1}{5} + \cos^2 \theta = 1 \implies \cos^2 \theta = 1 - \frac{1}{5} = \frac{4}{5}. \] Taking the square root, we find \( \cos \theta = -\frac{2}{\sqrt{5}} \) (negative in Quadrant II). Thus, the coordinates for point \( P \) on the terminal arm of angle \( \theta \) are: \[ P\left(-\frac{2}{\sqrt{5}}, \frac{1}{\sqrt{5}}\right). \] This means that point \( P \) lies in Quadrant II, reflecting the characteristics of angle \( \theta \).

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