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Units

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• The multitude of an angle is measured in the form of "multiple of unit angle".
  
  
• Public units for measuring multitude of angle are the following two:
  
  
  • Degree
    The angle u such that the multiple of u is the angle of the round.

• Radian
  The angle u defined as follows :

• The relation between degree and radian is as follows :

��raian �� 180 degree

Why : The multiple �� of the length of the arc �o�p is the length of the semicircle.�@Thus, The multiple �� of radian is the multitude of semi-round.