If we have the slope of $AB$ and $AC$. How can we determine the angle of $AB$ and $AC$?

If we have the slope of $$AB$$ and $$AC$$. How can we determine the angle of $$AB$$ and $$AC$$?

Let $$m$$ be the slope of AB and $$n$$ the slope of AC. The angle between them is $$|\arctan (m) - \arctan (n)|$$.