$\"\"$

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Find $\"\"$

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$\"\"$ inches, $\"\"$ inches, and $\"\"$ .

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Apply cosine law : $\"\"$ .

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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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$\"\"$ \ \

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$\"\"$ . $\"\"$

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The value of $\"\"$ .