Calculating Bearing from UTM (Latitude, Longitude) - geolocation

Question

I want to calculate the relative bearing between two geo-coordinate points. I've gone ahead and converted the coordinates to UTM, but need assistance on figuring out the actual bearing. I'm aware that UTM is only good enough for same-zone calculations, which is fine as the computation will be done across very small distances.
Say point1 is my location 44.4N,-97.7W
and point2 is the location I'd like to get the relative bearing to: 44.4N, -103.3W
Since point 2 is directly to the left of point 1, I'd interpret that as 270 degrees (North being 0 or 360 degrees).
I found this formula: arctan((y1-y2)/(x1-x2))
but it's result don't make sense to me when I plot the points and measure the angles.

Answer 1

FYI- For now, I'm using SQL Server 2008 Spatial Data Types, Spatial Functions, and some T-SQL function I found on the web.
ALTER FUNCTION dbo.GeographyBearing (
#Point1 geography,
#Point2 geography )
RETURNS FLOAT
AS
BEGIN
DECLARE #Bearing DECIMAL(18,15)
DECLARE #Lat1 FLOAT = RADIANS(#Point1.Lat)
DECLARE #Lat2 FLOAT = RADIANS(#Point2.Lat)
DECLARE #dLon FLOAT = RADIANS(#Point2.Long - #Point1.Long)
IF (#Point1.STEquals(#Point2) = 1)
SET #Bearing = NULL
ELSE
SET #Bearing = ATN2(
SIN(#dLon)*COS(#Lat2),
(COS(#Lat1)*SIN(#Lat2)) - (SIN(#Lat1)*COS(#Lat2)*COS(#dLon))
)
SET #Bearing = (DEGREES(#Bearing) + 360) % 360
RETURN ISNULL(#Bearing,0);
END
GO
DECLARE #Vienna geography = geography::Point(16.37, 48.21, 4326)
DECLARE #Moscow geography = geography::Point(37.60, 55.75, 4326)
SELECT dbo.GeographyBearing(#Vienna,#Moscow)

Answer 2

Please find here my answer related to an open source coordinates converter. It might be helpfull for you given your need.

Answer 3

My answer in Javascript http://jsfiddle.net/efwjames/NVhg6/
//stop location - the radii end point
var x1 = 44.9631;
var y1 = -93.2492;
//bus location from the southeast - the circle center
var x2 = 44.95517;
var y2 = -93.2427;
var radians = getAtan2((y1 - y2), (x1 - x2));
function getAtan2(y, x) {
return Math.atan2(y, x);
};
$("#output").text(radians);
var newdeg = radians * (180 / Math.PI);
$("#deg").append(newdeg);
var coordNames = ["N", "NE", "E", "SE", "S", "SW", "W", "NW", "N"];
var directionid = Math.round(newdeg / 45);
if (directionid < 0) {
directionid = directionid + 8
};
$("#dir").append("The vehicle is moving " + coordNames[directionid]);