I need an advice about learning directed angles

Question

Today I learned a bit about directed angles and to be honest it's not clear for me at all. Can someone suggest me any resources like books or videos to learn this thing deeply? Also I tried to search it on the web but only results I get are coterminal angles in trigonometry and I don't want this because in my book author (Evan Chen's Olympiad geometry) doesn't use directed angles as trigonometry subject.

Answer 1

Hint: Try to correlate directed angles in $\mathbb R^3$ to angle of inclination in $\mathbb R^2$. In $\mathbb R^2$ concept of directed angles is trivial because period of $\color{brown}{\tan x}$ is π .