title: Calculate the coord of the center of a circle knowing 2 points
body: <p><img src="https://i.stack.imgur.com/7x9P1.jpg" alt="oab"></p>
  
  <p>Hello, then I need to calculate the center of a circle O knowing 2 points A and B.
  I made a drawing because I am not able to explain in english.</p>
  
  <p>Thanks</p>