code: function getCircumCircle(p1, p2, p3) {
    var x1 = p1[0];
    var y1 = p1[1];
  
    var x2 = p2[0];
    var y2 = p2[1];
  
    var x3 = p3[0];
    var y3 = p3[1];
  
    //center of circle
    var D = 2 * (x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2));
  
    var Ux = ((x1 * x1 + y1 * y1) * (y2 - y3) + (x2 * x2 + y2 * y2) * (y3 - y1) + (x3 * x3 + y3 * y3) * (y1 - y2)) / D;
    var Uy = ((x1 * x1 + y1 * y1) * (x3 - x2) + (x2 * x2 + y2 * y2) * (x1 - x3) + (x3 * x3 + y3 * y3) * (x2 - x1)) / D;
  
    var px = Ux - x1;
    var py = Uy - y1;
    var r = Math.sqrt(px * px + py * py);
  
    return {
      cx: Ux,
      cy: Uy,
      radius: r
    };
  }
docs: Get circum circle of 3 points
  @param  {Object} p1 first point
  @param  {Object} p2 second point
  @param  {Object} p3 third point
  @return {Object} circumCircle