$\"\"$

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The vectors are $\"\"$ , $\"\"$ .

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$\"\"$ (Apply formula: $\"open$ )

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$\"\"$ (Simplify)

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$\"\"$ (Simplify) $\"\"$

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$\"\"$ (Apply formula: $\"open$ )

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$\"\"$ (Simplify)

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$\"\"$ (Simplify) \ \ $\"\"$

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$\"\"$ (Apply formula: $\"italic$ )

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$\"\"$ (Simplify)

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$\"\"$ (Simplify) $\"\"$

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The angle is $\"\"$ .