find shortrst distance betseen two points on earth in csharp

main.cs
public static double Distance(double lat1, double lon1, double lat2, double lon2)
{
    const double R = 6371; // Radius of the earth in 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 = R * c; // Distance in km
    return distance;
}

private static double ToRadians(double degrees)
{
    return degrees * Math.PI / 180;
}
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