How to find the angle between two points?

Question

JavaScript

I need to draw a line from point to point. I found out the length of the line, how now to get the angle of inclination?
https://jsfiddle.net/slavik_210/bvqLc3wx/13/

Answer 1

Strictly speaking, there can be no angle between two points.

Answer 2

Google is powerless in school puzzles?
Right Triangle Solution