Find the volume generated by rotating the region bounded by the given curves about the specified line. Express the answers in exact form or approximate to the number of decimal places indicated.
Find the volume of the solid generated by revolving the region bounded by the curve y = ln x, the x-axis, and the vertical line x=e². about the x-axis. (Express the answer in exact form.)

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Answer:

Step-by-step explanation:

Given that the region bounded by x axis, x=e^2 and y = lnx be rotated about x axis

The limits of x are [tex]1<x<e^2[/tex]

Volume generated = [tex]\int\limits^{e^2} _{1}  \pi {y^2} \, dx \\\\=\int\limits^{e^2} _{1}  \pi {(lnx)^2} \, dx \\\pi[x (lnx)^2 -\int\limits^{e^2} _{1} x(2lnx)dx]\\=2(e^1-1)\pi[/tex]

We will see that the volume is 46.403 cubic units.

How to find the volume?

The volume will be equal to 2*pi times the area of the region.

The area of the region is given by the integral of the function between the given interval, which is 0 < x < e^2

Then the area is given by:

[tex]A = \int\limits^{e^2}_0 {ln(x)} \, dx =( e^2*ln(e^2) - e^2 - 0*ln(0) + 0)\\\\\\A = e^2*ln(e^2) - e^2 = e^2 = 7.389[/tex]

To get the volume, we multiply that by 2*pi = 2*3.14, so we get:

V = (7.389)*2*3.14 = 46.403

So the volume is 46.403 cubic units.

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