------
## 最终结论
```python
import math

def distance_lat_long(lat1, lon1, lat2, lon2):
    R = 6371.0  # Earth radius in kilometers
    
    # Convert latitude and longitude from degrees to radians
    lat1_rad = math.radians(lat1)
    lon1_rad = math.radians(lon1)
    lat2_rad = math.radians(lat2)
    lon2_rad = math.radians(lon2)
    
    # Haversine formula
    dlon = lon2_rad - lon1_rad
    dlat = lat2_rad - lat1_rad
    
    a = math.sin(dlat / 2)**2 + math.cos(lat1_rad) * math.cos(lat2_rad) * math.sin(dlon / 2)**2
    c = 2 * math.asin(math.sqrt(a))
    
    distance = R * c
    return distance

# Test cases
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
```