How to calculate the direction of two AGSPoint

Question

I want to calculate the high precision direction of the two point ??The direction is calculated from the north of the earth.??. 
How can I do it by the SDK.
Thanks very much.

JamesZhang · Answer

http://www.mathsisfun.com/algebra/trig-finding-angle-right-triangle.html

Get the change in x and y for the 2 points, and use trigonometry to calculate the angle.

You may have to offset the angle to account for North being 0.

Thanks. 
This is a way to do. But higher latitude value may cause some error.

JamesZhang · Answer

Can you explain your problem a little in detail? I am not sure if I understood the meaning of calculating the direction of two points. A point does not have a direction associated with it. It is just a point.

Well, sorry for my poor English. I mean that:
Connecting two AGSPoint will make a straight line. Then the line will make a direction to the North of the Earth. (Just like the dirction of the compass)

RickJones · Answer

http://www.mathsisfun.com/algebra/trig-finding-angle-right-triangle.html

Get the change in x and y for the 2 points, and use trigonometry to calculate the angle.

You may have to offset the angle to account for North being 0.