$\"\"$

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The rate of change in radius is $\"\"$ .

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

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Differentiate on each side with respect to $\"\"$ .

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$\"\"$

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$\"\"$ .

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Substitute $\"\"$ in the derivative function.

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$\"\"$

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$\"\"$ .

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$\"\"$

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(a)

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Radius $\"\"$ .

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Substitute the radius $\"\"$ in the $\"\"$ .

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$\"\"$

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$\"\"$ .

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(b)

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Radius $\"\"$ .

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Substitute the radius $\"\"$ in the function $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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(a) $\"\"$ .

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(b) $\"\"$ .