When complex number represent stationary AC signal, it is called phasor. Complex number and so phasor can be presented with two equivalent notifications:

- Cartesian coordinates
- Polar coordinates

Knowing exponential representative of complex number, we have relation between complex number and trigonometric functions as

So, if we have two sine or cosine signals with some phase, it is easy to obtain their sum or difference via Cartesian coordinates of AC signal complex representatives. Online addition and subtraction of complex numbers together with time domain waveforms can be done on following links:

phasor i.e. complex number addition

phasor i.e. complex number subtraction

In AC electrical theory we need to add two or more trigonometric currents that flow in/from given node, or to add two or more trigonometric voltages. Utilization of phasor for that purpose is very practical thing.

**External links:**

Phasor addition and phasor subtraction on Wikipedia

Phasor addition and phasor subtraction on Wikibooks

Phasor addition and phasor subtraction on Regentsprep

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