By constructing two circles with the same radius, it can be proved that all four points are circles, in which one circle consists of four given points, the other is outside the first circle, one point is on the first circle and the other three points are on the second circle. Another proof method is to use the "principle of proportion", that is, in a triangle composed of four points, the ratio of adjacent sides is equal to the ratio of diagonal to adjacent sides, indicating that the triangle is an isosceles triangle with four points on the same circle.