Problem

Use the shell method to find the volume generated by revolving the shaded region about the y-axis.
Set up the integral that gives the volume of the solid.

Answer

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Answer

Therefore, the total volume of the solid is 5π+12π=17π cubic units.

Steps

Step 1 :The shaded region can be divided into two parts: a rectangle with a height of 5 units and a width of 1 unit, and a rectangle with a height of 2 units and a width of 3 units.

Step 2 :The volume of the solid generated by revolving the first rectangle about the y-axis can be calculated using the shell method. The formula for the volume of a cylindrical shell is 2πrh, where r is the distance from the axis of rotation to the center of the shell, and h is the height of the shell. In this case, r varies from 0 to 1, and h is always 5. So the volume is 012πrhdr=012πr(5)dr=10π01rdr=10π[12r2]01=5π cubic units.

Step 3 :The volume of the solid generated by revolving the second rectangle about the y-axis can be calculated in a similar way. In this case, r varies from 1 to 4, and h is always 2. So the volume is 142πrhdr=142πr(2)dr=4π14rdr=4π[12r2]14=4π(12(421))=12π cubic units.

Step 4 :Therefore, the total volume of the solid is 5π+12π=17π cubic units.

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