Before discussing these any further, it is useful to review the concept of phasors, particularly because we will use phasors
in conjunction with vector variables.
The phasor notation is a method of representing complex numbers. Consider a complex number b ¼ u0 + jv0, where
j ¼
ffiffiffiffiffiffiffi
1 p : The complex number b can be represented in a plane, called a complex plane, as in Figure 11.4a. The real part of
b is u0, and it is the projection of b on the real axis, whereas the imaginary part of a is vo and represents its projection on the
imaginary axis.
Instead of writing b in the above form, we can also write b in terms of a magnitude and an angle. The phasor notation is
based on the latter form and arises from Euler’s equation: