$\"\"$

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Two sides of the triangle are $\"\"$ and $\"\"$ .

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The angle of triangle $\"\"$ .

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Solve the triangle by using Law of cosines formula: $\"\"$ .

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

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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Find other two angles, by using law of cosines formula: $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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The sum of three angles in a triangle

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$\"\"$

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$\"\"$

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