code: def angular_dist_to_euclidean_dist(D, r=1):
      """convert angular distances to euclidean distances"""
      return 2 * r * np.sin(0.5 * D * np.pi / 180.0)
  
file_path: astroML/astroML/correlation.py
imports: import numpy
  from sklearn.neighbors import KDTree
  from sklearn.utils import check_random_state
label_desc: Use image node_id 3 for calling a global function with example usage: angular_dist_to_euclidean_dist(D, r) and returns: unknown