TITLE: Can I find the magnetic heading from A to B on triangle ABC if the lengths and angles inside the triangle are known?
QUESTION [0 upvotes]: 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?

REPLY [0 votes]: If the lengths are know, the angles of the triangle are known as well.  But you have not described any information that would allow determining the rotation of the triangle in the plane.  Imagine rotating the triangle around A by 15 degrees clockwise-that will change the compass heading but nothing in your data.
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