Calculate angle between two Latitude/Longitude points

Question

Is there a way to calculate angle between two Latitude/Longitude points?

What I am trying to achieve is to know where the user is heading. For example, user is head

Answer 1

In case someone need PHP code for this functionality:

/**
 * Calculate angle between 2 given latLng
 * @param  float $lat1
 * @param  float $lat2
 * @param  float $lng1
 * @param  float $lng2
 * @return integer
 */
function angle($lat1, $lat2, $lng1, $lng2) {
    $dLon = $lng2 - $lng1;
    $y = sin($dLon) * cos($lat2);
    $x = cos($lat1) * sin($lat2) - sin($lat1) * cos($lat2) * cos($dLon);
    return 360 - ((rad2deg(atan2($y, $x)) + 360) % 360);
}