$\"\"$

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The center of the sphere is $\"\"$ and radius is $\"\"$ .

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Equation of a sphere:

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An equation of a sphere with center $\"\"$ and radius is $\"\"$ is $\"\"$ .

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Here $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$ .

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The equation of the sphere is $\"\"$ .

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$\"\"$

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Find the intersection of the sphere with $\"\"$ -plane.

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In $\"\"$ - plane, $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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Therefore, a circle is the intersection of $\"\"$ -plane.

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$\"\"$

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The equation of the sphere is $\"\"$ .

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The circle $\"\"$ is the intersection of $\"\"$ -plane.