Polar form
From AoPSWiki
Polar form for complex numbers
The polar form for complex numbers allows us to graph complex numbers given an angle 
and a radius or magnitude 
.
For 
, we can write 
. (See cis if you do not understand this notation.) This represents a complex number 
that is units away from the origin, and radians counterclockwise from the positive half of the 
-axis.
