As we know, the central angle of a circle 1/360 is called 1 degree angle, which is recorded as 1 degree, 1 degree =60 minutes (1 degree = 60'), and 1 minute is equal to 60 seconds.

Because the angle system is hexadecimal, it is often difficult to convert units when calculating the addition and subtraction of two angles. Therefore, in mathematics and scientific research, another method is often used to measure angles: the central angle of an arc with a long radius is called 1 radian angle, and it is recorded as 1(rad).