$\"\"$

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Differentiation rule :

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Suppose $\"\"$ and $\"\"$ are differentiable vector functions, $\"\"$ is a scalar and $\"\"$ is a real valued function.

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Then $\"\"$ .

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$\"\"$

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Consider the vector $\"\"$ and $\"\"$ .

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$\"\"$ .

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$\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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Find the value of $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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Therefore, $\"\"$ .

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$\"\"$

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$\"\"$ .