Question Use the disk method to find the volume of the solid of revolution bounded by the \( x \)-axis and the graphs of \( f(x)=3 \sqrt{6 \sin x}, x=\frac{2 \pi}{3} \), and \( x=\pi \) rotated about the \( x \)-axis. Enter your answer in terms of \( \pi \).
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To find the volume of the solid of revolution using the disk method, we start by identifying the bounds of integration which are \( x = \frac{2\pi}{3} \) and \( x = \pi \). The volume \( V \) is given by the integral: \[ V = \pi \int_{a}^{b} [f(x)]^2 \, dx \] Substituting our function \( f(x) = 3 \sqrt{6 \sin x} \) into the formula gives: \[ V = \pi \int_{\frac{2\pi}{3}}^{\pi} [3 \sqrt{6 \sin x}]^2 \, dx \] This simplifies to: \[ V = \pi \int_{\frac{2\pi}{3}}^{\pi} 54 \sin x \, dx \] Now we compute the integral: \[ V = 54\pi \int_{\frac{2\pi}{3}}^{\pi} \sin x \, dx \] The integral of \( \sin x \) is \( -\cos x \), so we evaluate the definite integral from \( \frac{2\pi}{3} \) to \( \pi \): \[ V = 54\pi \left[-\cos x\right]_{\frac{2\pi}{3}}^{\pi} \] Calculating the boundaries: \[ = 54\pi \left[(-\cos(\pi)) - (-\cos(\frac{2\pi}{3}))\right] \] \[ = 54\pi [1 - \left(-\frac{1}{2}\right)] \] \[ = 54\pi \left(\frac{3}{2}\right) \] \[ = 81\pi \] Therefore, the volume of the solid of revolution is: \[ \boxed{81\pi} \]