Laws of Sines and Cosines

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The following laws hold for any triangle with sides and angles labeled as shown below.

Law of Sines

$$\frac{a}{\sin A}=\frac{b}{\sin B}=\frac{c}{\sin C}$$

Law of Cosines

$$\begin{array}{rl}& \\ a^2& =b^2+c^2-2bc\cos A\\ b^2& =a^2+c^2-2ac\cos B\\ c^2& =a^2+b^2-2ab\cos C\end{array}$$