text: import math as _math
  
  
  EARTH_RADIUS = 6371
  
  
  def rad2deg(x):
      return x * 360 / (2 * _math.pi)
  
  
  def deg2rad(x):
      return x * 2 * _math.pi / 360
  
  
  def angle(a, b):
      return _math.acos(a.dot(b) / a.length / b.length)