Derive from the following formulae that calculate the angle for the whole circle:
$$ \theta = \frac{s}{r} = \frac{2\pi r}{r} = 2\pi = 360\degree $$
Where \(s\) is the circumference of the circle, \(r\) is the radius of the circle.
We know that \(\pi = 180\degree\). The former is in radian, the latter is in degree. Both express the same idea, just in different units. Therefore, it is quite easy to convert them interchangeably.