Q. The region between the curvey=secx,0≤x≤4πand the x-axis is revolved about the x-axis to generate a solid.Find the exact value of its volume.
Disk Method Integration: To find the volume of the solid, we use the disk method, which involves integrating the area of circular disks along the x-axis from x=0 to x=4π.
Area of Disk Calculation: The area of a disk at a particular x is given by A(x)=π[sec(x)]2, since the radius of the disk is the y-value of the function, which is sec(x).
Volume Integral Calculation: The volume V is the integral of A(x) from x=0 to x=4π. So, V=∫04ππ[sec(x)]2dx.
Integral Evaluation: Now we calculate the integral: V=π∫04πsec2(x)dx.
Final Volume Calculation: The antiderivative of sec2(x) is tan(x), so we evaluate tan(x) from 0 to (π)/(4).
Final Volume Calculation: The antiderivative of sec2(x) is tan(x), so we evaluate tan(x) from 0 to 4π.Evaluating the antiderivative at the bounds gives us V=π[tan(4π)−tan(0)].
Final Volume Calculation: The antiderivative of sec2(x) is tan(x), so we evaluate tan(x) from 0 to (π)/(4). Evaluating the antiderivative at the bounds gives us V=π[tan((π)/(4))−tan(0)]. Since tan((π)/(4))=1 and tan(0)=0, we have V=π[1−0].
Final Volume Calculation: The antiderivative of sec2(x) is tan(x), so we evaluate tan(x) from 0 to (π)/(4). Evaluating the antiderivative at the bounds gives us V=π[tan((π)/(4))−tan(0)]. Since tan((π)/(4))=1 and tan(0)=0, we have V=π[1−0]. Therefore, the volume V=π cubic units.
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