In the first grade of primary school, the graphic elbow of mathematical robot is round. The robot is presented as a plan, and the joints of the arms are replaced by circles. There are two definitions of a circle. The first definition of a circle: the set of points whose distance to a fixed point in the same plane is equal to a fixed length is called a circle, and this fixed point is called the center of the circle; The second definition of a circle: the ratio of the distance between a moving point and two fixed points on a plane (or the ratio of the square of the distance) is equal to a constant that is not 1, and the trajectory of the moving point is a circle.