rad → turn
Babylonians divided circles into 360 parts around 1500 BCE, possibly based on their calendar having ~360 days.
The radian wasn't formally defined until 1714 by Roger Cotes, but was used by mathematicians for centuries before getting a name.
The Antikythera mechanism used geared angles to predict eclipses - ancient Greeks had sophisticated angular calculations.
GPS and astronomy use degrees/minutes/seconds (DMS): 40°26'46" N. Computer graphics prefer radians for calculations.
Why was the obtuse angle always upset? Because it was never right! 📐