$\"\"$

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The sides of the triangle are $\"\"$ , $\"\"$ an $\"\"$ .

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Find the three angles by using the Cosine Law.

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Cosine law: $\"\"$ .

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$\"\"$

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Substitute $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

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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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Cosine law: $\"\"$ .

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$\"\"$ .

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Substitute $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

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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 sum of angles in a triangle is $\"\"$ .

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Substitute $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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The angles are $\"\"$ , $\"\"$ and $\"\"$ .

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$\"\"$

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The angles are $\"\"$ , $\"\"$ and $\"\"$ .