Complex Polar Coordinate
[Polar Coordinate](https://texonom.com/polar-coordinate-affa11aeb26241cdabf2a592e73daf91) 


### Normal Coordinate
$R + Ii$ can be expressed in normal coordinate $(R, I)$
### Polar Coordinate
let $\theta = tan^{-1}\frac{I}{R}, r = \sqrt{R^2+I^2}$, then $R + Ii = r(cos\theta + isin\theta)$
by [Euler's Formula](https://texonom.com/eulers-formula-71f5337221904ba5b26e1398af5de0ab) $r(cos\theta + isin\theta) = re^{j\theta}$








