Revising for Exams: Understanding Euler Formula #8

[Monochrome]

I'm doing revision for next semesters exams and I ran across this:

http://mathworld.wolfram.com/EulerFormula.html

Specifically formula no.8. I've seen it before but can't find it in my notes, I forgot what splitting

$${\frac {d z}{d\theta}}$$

on either side of the equals sign was called. But I do remember being warned not to think that it is just division.

 

[HallsofIvy]

That is "separating" the differential. What you have is a "separable" differential equation and you separated the variables.