Precalculus - Unit 3: Complex Numbers - suddenly using e?

Hi, submitting some feedback regarding the content/organization of the Precalculus course.

Everything has been going quite smoothly until I hit Unit 3: Complex Numbers.

The first thing I noticed was that it doesn't feel like there's a lot of conceptual dots being connected between some of the Trigonometry being used and the Complex Plane. That's all well and good, I went and watched a few lectures on YT to fill in some gaps.

However, it seemed like e was suddenly being used in solutions on Lesson 8 "Complex number equations: x^3=1"

I also recalled seeing "Exponential ... r * e^(i * theta)" back in U3L6: Complex number forms review (article). I don't recall there being a detailed explanation back then either, but noted it as "maybe that will be better explained later?"

Not sure if I missed a video in a previous course that explains the seemingly sudden use of e or if there's a video coming later that will help connect the dots, but at the moment it's very confusing.