The complex amplitude is also defined as the phasor associated with any sinusoid having amplitude and phase . The term ``phasor'' is more general than ``complex amplitude'', however, because it also applies to the corresponding real sinusoid given by the real part of Equations (1.9-1.10). In other words, the real sinusoids and may be expressed as
and is the associated phasor in each case. Thus, we say that the phasor representation of is . Phasor analysis is often used to analyze linear time-invariant systems such as analog electrical circuits.
Plotting Complex Sinusoids as Circular Motion