i'm trying to create a simple navigator, with an arrow that indicate the direction from the location where i'm to the location saved in the map, like a compass with north. i've two location (long and lat), start point and final point. The arrow must rotate from north to the final point direction. I need to calculate this movement i degrees. It's like two side of a triangle, and the movement is the interior angle.
How can calculate this angle, knowing the two distance?