Analysis of test questions: (1) Just draw according to the intersection of the perpendicular lines of any two strings in the circle as the center of the circle;

(2) It can be solved according to the properties of tangent and Pythagorean theorem.

(1) As shown below, the center of the circle is P (2 2,0).

(2)∵ ?

∴ .

Comments: Drawing ability is the basic ability in junior high school mathematics learning. The senior high school entrance examination is common, generally not difficult, and needs to be mastered skillfully.