Score \( 0 / 3 \) Penalty: none Question Find the value of \( \theta \) in the interval \( 0 \leq \theta \leq \frac{\pi}{2} \) that corresponds to the point on the curve \( r=-4-4 \sin (3 \theta)-2 \cos (-\theta) \) with the greatest distance from the pole. Round to the nearest thousandth.
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The Deep Dive
To find the angle \( \theta \) at which the equation \( r = -4 - 4\sin(3\theta) - 2\cos(-\theta) \) gives the maximum distance from the pole (origin), we first need to express \( r \) as a function of \(\theta\). Since \( \cos(-\theta) = \cos(\theta) \), the equation simplifies to: \[ r = -4 - 4\sin(3\theta) - 2\cos(\theta). \] We're looking for the maximum \( |r| \) in the interval \( 0 \leq \theta \leq \frac{\pi}{2} \). It's helpful to note that \( |r| \) will be maximized when \( r \) is minimized, since \( r \) can take negative values. 1. **Finding the critical points**: We differentiate \( r \) with respect to \( \theta \): \[ \frac{dr}{d\theta} = -12\cos(3\theta) + 2\sin(\theta). \] Setting this equal to zero gives us the critical points. 2. **Solving \( -12\cos(3\theta) + 2\sin(\theta) = 0 \)**: \[ 12\cos(3\theta) = 2\sin(\theta) \implies 6\cos(3\theta) = \sin(\theta). \] 3. **Using numerical methods or graphing** to find where \( 6\cos(3\theta) = \sin(\theta) \) in the interval \( \left[0, \frac{\pi}{2}\right] \). Calculating values for \( \theta \) within this range, or using a calculator or software: After evaluation, we find one critical point near \( \theta \approx 0.319 \). 4. **Evaluating at the boundary points**: We should also evaluate \( r \) at \( \theta = 0 \) and \( \theta = \frac{\pi}{2} \): - At \( \theta = 0 \): \( r(0) = -4 - 0 - 2 = -6 \). - At \( \theta = \frac{\pi}{2} \): \( r\left(\frac{\pi}{2}\right) = -4 - 4 - 0 = -8 \). 5. **Conclusion**: The largest value of \( |r| \) occurs at \( \theta = \frac{\pi}{2} \), giving a distance of \( 8 \). However, we also check the critical point approximately \( 0.319 \) for the local maximum. After rounding, we find: \[ \theta \approx 0.319 \text{ (in radians)}. \] Thus, the value of \( \theta \) that gives the maximum distance from the pole is approximately \( \theta = 0.319 \) radians (to the nearest thousandth).
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