code: function getAngle(touch1, touch2) {
        var y = touch2.pageY - touch1.pageY,
        x = touch2.pageX - touch1.pageX;
        return Math.atan2(y, x) * 180 / Math.PI;
      }
docs: calculate the angle between two coordinates
  @param   {Touch}     touch1
  @param   {Touch}     touch2
  @returns {Number}    angle