Question: 
Write a function to calculate distance between two points using latitude and longitude.


Model's Code:
def distance_lat_long(lat1, lon1, lat2, lon2):
    import math
    R = 6371.0  # Radius of the Earth in kilometers
    dlat = math.radians(lat2 - lat1)
    dlon = math.radians(lon2 - lon1)
    a = (math.sin(dlat / 2) ** 2 +
         math.cos(math.radians(lat1)) * math.cos(math.radians(lat2)) * 
         math.sin(dlon / 2) ** 2)
    c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a))
    distance = R * c
    return distance



Sample Correct Code:
from math import radians, sin, cos, acos
def distance_lat_long(slat,slon,elat,elon):
 dist = 6371.01 * acos(sin(slat)*sin(elat) + cos(slat)*cos(elat)*cos(slon - elon))
 return dist


Asserts:
assert distance_lat_long(23.5,67.5,25.5,69.5)==12179.372041317429
assert distance_lat_long(10.5,20.5,30.5,40.5)==6069.397933300514
assert distance_lat_long(10,20,30,40)==6783.751974994595


Tests:
Test 1 of 3: FAIL: AssertionError()

Test 180 of 974: 133/180 (73.88888888888889%): failed