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Math Help - Law of Cosine

  1. #1
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    Law of Cosine

    Hey if you have a triangle with one side 25. another side 25. and the bottom side 30. You just use law of cosines to figure out the answer to finding an angle with the triangle?
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  2. #2
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    a^{2}=b^{2}+c^{2}-2bc\cos A

    \cos A=\frac{b^{2}+c^{2}-a^{2}}{2bc}

    b^{2}=a^{\text{2}}+c^{2}-2ac\cos B

    \cos B=\frac{a^{2}+c^{2}-b^{2}}{2ac}

    c^{2}=a^{2}+b^{2}-2ab\cos C

    \cos C=\frac{a^{2}+b^{2}-c^{2}}{2ab}
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  3. #3
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    Quote Originally Posted by zachcumer View Post
    Hey if you have a triangle with one side 25. another side 25. and the bottom side 30. You just use law of cosines to figure out the answer to finding an angle with the triangle?
    In general your suggestion is OK. But your triangle is an isosceles triangle which can be split into 2 right triangles.

    Then calculations are much easier to do.
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