$\"\"$

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The angle of the triangle $\"\"$ .

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The two sides of the triangle is $\"\"$ and $\"\"$ .

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Find the side $\"\"$ by using law of cosines.

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Law of cosines: $\"\"$ .

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

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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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Find the angle $\"\"$ by using law of sines.

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Law of sines: $\"\"$ .

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Consider $\"\"$ .

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

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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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Sum of the three angles in a triangle $\"\"$ .

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$\"\"$

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Substitute $\"\"$ and $\"\"$ in above expression.

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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