title: How to Find Dot Product of Two Lines (Opencv)
body: <p>I'm working on a program that require me to find the angle between two lines. I have found all of the points coordinates of the lines, referenced into the 0,0 points, but i dont understand how to implement the dot product in Opencv to find the angle. </p>
  
  <p>I use visual C++ using opencv library. I also found out that i can use cv::Mat::dot function to get dot product, but i can't find any good example. I can not understand the explanation in this <a href="http://docs.opencv.org/modules/core/doc/basic_structures.html?highlight=dot#double%20Mat%3a%3adot%28InputArray%20m%29%20const" rel="nofollow">link</a>.</p>
  
  <p>Can anyone give me a good example? so i can understand how to use that function to find dot product of two lines. Thank you. </p>