Complex numbers are made up of both a real and an imaginary part. The letter "j" is used here to represent the imaginary operator because it is the most common form found in engineering works. Mathematicians and physicists like to use the letter "i."

Basic Properties		if n = a + jb = c /θ, then:
Euler's Identity		Rules
Where "j" (or "i") is the imaginary operator, and * designates the complex conjugate