One degree (shown in red) and 89 degrees (shown in blue)
|Unit system||Non-SI accepted unit|
|Symbol||° or deg|
|1 ° in ...||... is equal to ...|
The actual reason of choosing the degree as a way to measure plane angle is unknown. One theory says that it is related with the fact that a year is approximately 360 days. Some ancient calendars, for example the Persian calendar, used 360 days for a year.
Another theory says that the Babylonians divided the circle using the angle of an equilateral triangle. The angle was then divided into 60 parts. This is because they used sexagesimal or base-60 numeral system.
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