[Closed] Simple angle calculation – why wrong?

Hi! I have this simple formula to calculate angle between 2 points:

theAngle = acos(dot (normalize p1) (normalize p2))

Now, I get 2 points from UVW elements selection. I want to track its rotations. So, lets say, I get angle 24 from the very start.

Then I take my selected UVW eleement, scale it down.

theAngle value is now 14! But why? I just scaled it down, no rotation so far. So I assumed relative rotation between 2 points of element would stay the same?