float dist1cosine = cos(25.0 / EARTH_RADIUS);
  float dist2cosine = cos(50.0 / EARTH_RADIUS);
  float dist3cosine = cos(75.0 / EARTH_RADIUS);
  while (read_from_file(&newzip, &newlat, &newlon)) {
    mydistcos = great_circle_distance_cosine(newlat,newlon,
                                             origlat,origlon);
    if (mydistcos >= dist1cosine)
    {
      // do stuff to add it to file
    }
    if (mydistcos >= dist2cosine)
    {
      ...
    }
    ...
  }