title: Calculating the angle between Points
body: <p>Working with C++ and opencv</p>
  
  <p>I am trying to calculate an angle between two points.....I have a 2D plane with a changing center point of a bounding box, Now if the center point in frame 1 has changed its location in frame 2 i need to find the angle of these two points. </p>
  
  <p>Here is the example of what i am trying to do:</p>
  
  <p><img src="https://i.stack.imgur.com/1tgcj.jpg" alt="enter image description here"></p>
  
  <p>Can someone suggest a way of working this out.......? some kind of mathematical solution or perhaps a C++ function.</p>