Determine angle between 3 points.

[MyFriendIsATaco]

I have 3 points, A, B, and C. They are placed to form angle ABC. How can I calculate what that angle is? I will have x and y positions for all points. Mind you: NOT a right triangle.

I tried Googling about it, and didn't really find anything, so any insight would be awesome. My highschool math is a little dusty! :P

Many thanks!

[kortex]

http://www.friendsofed.com/samples/1590595181.pdf

about page 319

[Eager Beaver]

Please see this FLA.
Properties of a Triangle.

[Tormenter]

The maths formula for the included angle is:

ca*ca=ab*ab+bc*bc-2*ab*bc*Math.cos(B);

where B is in radians.
B in degrees is:

Bdeg=Brad*180/Math.PI;