Magnitude of a Complex Number
Complex numbers include real numbers as well as the imaginary number j, which represents $ \sqrt{-1} $.
Complex numbers are harder to deal with than real numbers because of the two parts they contain, real and imaginary. Simple operations like finding the absolute value (aka. Magnitude or Norm) are more difficult.
Magnitude of complex number z = |z| = $ \sqrt{Re(z)^2 + Im(z)^2} $
