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Toolkit 58

Law of Cosines

Triangle ABC with sides a, b, c

For a triangle with sides aa, bb, cc:

a2=b2+c2−2bccos⁡Aa^2=b^2+c^2-2bc\cos A

or

cos⁡A=b2+c2−a22bc\cos A=\frac{b^2+c^2-a^2}{2bc}
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