I want to find the magnetic heading (from north) from a point $A$ to a point $B$ on a $\triangle ABC$. $A, B and C$ are moving and so the angles can be any value. as an example, the triangle could be this shape.
Lengths $a, b$ and $c$ are known and therefore using the law of cosines the angles at A, B and C can be found. Is there a way to use these values to find the magnetic heading or is it completely removed from these angles?