Complex number z = x + iy is taught in middle school, however the deduced theory by Euler is new for me,

It is deduced from Tayler series:

Plugging in x = pie, we get the famous most beautiful Euler’s equation: e^ipie + 1 = 0

Commonly used complex formulas are as follows

As is stated in the preceding blog, there is a way to unite expression in cartisian and polar systems

The advantage of using polar form is that it’s much easier in multiplication of complex numbers