Add radius to Longitude and Latitude with C#

I need to generate a bounding box of min and max latitude and longitude values so I can return addresses within a given radius.

I have two func<>'s below to return the range I need to +/- to the lon lat coordinates to establish the bounding box. However I don't think the math is 100%

I am using the Haversine formula to generate my distance calculations and that seems to be working accurately. I investigated the Vincenty formula for distance as well but for my needs that was overkill.

My problem is that I would like my search results to be as accurate as Haversine in that the range I +/- to the lon lat coordinates takes开发者_StackOverflow into account the ellipsoidal curvature or the earth.

Ok, here are my func<>'s...please note I am not a Math professor :o)

static Func<double, int, double> GetLatitudeRange = (latitude, distance) => (180.0 / Math.PI) * (distance / EARTH_RADIUS_IN_KM);


static Func<double, double, int, double> GetLongitudeRange = (longitude, latitude, distance) =>
            (
                Math.Asin(
                    Math.Sin(distance / EARTH_RADIUS_IN_KM) / Math.Cos(latitude)
                    )
            );

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