Answer:
Cosine
Step-by-step explanation:
If the triangle is not right-angled, and there is not a matching pair, you will need the Cosine Rule..
and the formula used will be: [tex]a^2 = b^2 + c^2 - 2 b c cos A[/tex]
In the opposite case if the triangle is not right-angled, and there is a matching pair, you will need the Sine Rule..