There are two ways to represent a complex number:
x + iy
r (cos φ + i sin φ)
Both of these ways are equivalent since:
Here is the Argand Diagram:
One important point to remember is that in the r (cos φ + i sin φ) form, all values can be positive since r is an absolute magnitude and φ is a value between 0 and 2π using radians (or in degrees, between 0 and 360).
- Complex Number, Wikipedia