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

Question

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

I searched the internet but I don’t understand. Please help! Thank you very much.

Answer 1

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