a function for calculating distance between lat long in csharp

main.cs
public static double Distance(double lat1, double lon1, double lat2, double lon2)
{
    const double earthRadius = 6371; // km
    
    var dLat = ToRadians(lat2 - lat1);
    var dLon = ToRadians(lon2 - lon1);
    
    var a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +
        Math.Cos(ToRadians(lat1)) * Math.Cos(ToRadians(lat2)) *
        Math.Sin(dLon / 2) * Math.Sin(dLon / 2);
    var c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
    var distance = earthRadius * c;
    
    return distance;
}

private static double ToRadians(double degrees)
{
    return degrees * Math.PI / 180;
}
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main.cs
var distance = Distance(51.5074, -0.1278, 40.7128, -74.0060); // London to New York
Console.WriteLine(distance); // Output: 5572.169
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