# Origin of phase angle nomenclature?

1. Feb 13, 2013

### joema

It's common to express phase differences between two sinusoidal waveforms as a "phase angle", with a full cycle corresponding to 360 degrees.

What is the origin of this nomenclature, and why is phase expressed in degrees?

Examined naively, the time domain representation of two waveforms has no obvious relationship to angular degrees.

2. Feb 13, 2013

### sophiecentaur

Waveforms are often described in terms of the sum of sin and cos waves, the most basic being
A=A0(sin(ωt+∅))
The argument of trig functions is an angle, in radians, strictly but at a simple level, we can use degrees. ω is the 'angular frequency' and its value is 2∏f, where f is the frequency (in Hz or cycles per second).
Strictly, the term 'phase' only refers to continuous (or long lasting) waveforms. If you are describing short bursts or pulses then any time shift or difference is measured in units of time.
I suggest you read around the topic and just take note of the way its discussed - you will soon become accustomed to the usage.

3. Feb 22, 2013

### jsgruszynski

Also ALL of analog electronics/circuits is based on complex numbers and trigonometry so you are going to have angles all over the place.