title: Is there any way to convert a vector to euler angle?
body: <p>I have 2 vectors in 3D space, for example:</p>
  
  <p><img src="https://i.stack.imgur.com/xVt1q.png" alt="enter image description here"></p>
  
  <p>If I know these 4 points, is there any method to find out the euler angles of them? 
  I am trying to move these two vectors to the origin, then assuming these two vectors are rotated from two reference vector, which have the same length of these two, for example (0,0,z1),(0,0,z2). But I do not know what to do next. Am I in the right way, or is there any other method to find out the euler angles?</p>
  
  <p>BTW: I have got some ideas from <a href="https://stackoverflow.com/questions/35613741/convert-2-3d-points-to-directional-vectors-to-euler-angles/35675525#35675525">this answer</a>  but I do not know the meaning of the final matrix :(</p>