According to G. Pólya, the method of finding geometric objects by intersection. 1. For example, the centers of all circles tangent to a straight line s at a given point P lie on a line t that passes through P and is perpendicular to s. 2. In addition, the circle c centered at P with radius R is the locus of the centers of all circles of radius R passing through P. The intersection of c and t consists of two points A and B which are the centers of two circles of radius R tangent to s at P.