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Question

Find the volume of the solid generated by revolving the region bounded by the graphs of the equations about the x-axis. y=cos 2x, y=0, x=0, x=π/4

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Answered 9 months ago
Answered 9 months ago
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To find the Volume\textbf{Volume} of the solid given we will apply The Disk Method\textbf{The Disk Method} ...

V=πabR(x)2dx\boxed{\color{#c34632}{V=\pi\int_{a}^{b}{R(x)^2dx}}}

From the exercise given we can see that we need to find

V=π0π/4(cos(2x))2dx\begin{equation} V=\pi\int_{0}^{\pi/4}{(\cos{(2x)})^2dx} \end{equation}

This leads\textbf{This leads} to:

V=π0π/4cos(4x)12dx=π20π/4(cos(4x)1)dx=π2[sin(4x)4+x]0π/4=π28\begin{align*} V&=\pi\int_{0}^{\pi/4}{\frac{\cos{(4x)}-1}{2}dx}\\ &=\frac{\pi}{2}\int_{0}^{\pi/4}{(\cos{(4x)}-1)dx}\\ &=\frac{\pi}{2}\left[\frac{\sin{(4x)}}{4}+x\right]_{0}^{\pi/4}\\ &=\frac{\pi^2}{8}\\ \end{align*}

So, our final answer\textbf{final answer} is:

π28\boxed{\color{#c34632}{\frac{\pi^2}{8}}}

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