$\"\"$

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Therom of Pappus :

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Let $\"\"$ be a region in a plane and and let $\"\"$ be the same plane such that L does not intersect with the interior of $\"\"$ .

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If $\"\"$ is the distance between centeriod $\"\"$ and the line then the volume $\"\"$ of the solid of the revolution formed by revolving $\"\"$ about the line is $\"\"$ .

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$\"\"$

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The region is $\"\"$ .

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Radius of the circle $\"\"$ .

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Area of the circle is $\"\"$ .

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Volume $\"\"$ of the solid of the revolution formed by revolving $\"\"$ about the line is $\"\"$ .

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Where $\"\"$ , distance between center of circle and $\"\"$ -axis.

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Area $\"\"$ .

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Now find the volume by substituting the values in the formula $\"\"$ .

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$\"\"$

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$\"\"$

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The torus formed by revolving the circle $\"\"$ about the $\"\"$ -axis is $\"\"$ .