$\"\"$

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Consider the vectors are $\"\"$ 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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The dot product of $\"\"$ 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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Therefore, $\"\"$ .

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$\"\"$

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$\"\"$ .