Loading subject…
Cosine rule
A formula for any triangle that relates a side length to the other two side lengths and the cosine of the included angle. For triangle $ABC$: $a^{2}=b^{2}+c^{2}-2bc\cos A$ (and similarly for $b$ and $c$).
Sine rule
For any triangle $ABC$, $$\frac{\sin A}{a}=\frac{\sin B}{b}=\frac{\sin C}{c}$$
Equivalently, $$\frac{a}{\sin A}=\frac{b}{\sin B}=\frac{c}{\sin C}$$