How is an angle's degree determined?

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To be as specific as possible I am not asking the following:

  • What is a degree? (Measurement of rotation between two intersecting rays/lines)
  • How much is a degree? ($\frac{1}{360}$th rotation of a circle)
  • How do you measure an angle in degrees with a protractor?

I've Googled and watched several Youtube videos regarding this question and they all say something along the lines of the items I listed.

Similar to how a Radian is found with radius and arc length, how is a degree found with just the information gathered from an angle (i.e the ray length and the arc length)?

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If you have convinced yourself that a Radian is how much of a turn is required so that the resulting arc length is equal to the radius of the resulting circle...

then a Degree is how much of a turn is required so that the resulting arc length is equal to $\frac 1{360}$ of the circumference of resulting circle.

The identities:

$C = 2\pi r$.

$arc = r\times rad$.

$arc = \frac {degrees}{360}\times C$

$rad = \frac {arc}{r}$.

$degree = \frac {arc}{C}\times 360$.

$degree = \frac {360}{2\pi} rad = \frac {180}{\pi} rad$.

$rad = \frac {\pi}{180} degree$.

Of course, you are assuming arc length, radius and circumference is known. Often the arc length is not known but the proportion of a rotation (whether you consider a rotation to be $2\pi$ radians or $360^\circ$) is known.