title: Given two square points (x, y) find the other two to draw the square
body: <p>I'm having difficulties to draw a square given two points only.</p>
  
  <p>For example if I have A (4,4) and B (5,0) I need to draw the square by pressing SHIFT (the orientation of the square is given by the position of the mouse after SFHIT has been click).</p>
  
  <p>I have the equation y = m*x + b of the line (4,4) -> (5,0) and I can know if the mouse is above or below the line in that specific moment. </p>
  
  <p>My diffculty is to find the other two vertices, so that, I can draw the lines and have a square.</p>
  
  <p>I know that this is more Maths than programming, or better, is all about maths, but i would apreciate if someone can help me.</p>
  
  <p>Thanks</p>