在平面直角坐标系中,以(a,b)为圆心,r为半径的圆的方程是(x-a)2+(y-b)2=r2.若r=0,则上述标准方程变为(x-a)2+(y-b)2=0.此式表示的图形是平面直角坐标系中一个孤立的点C(a,b),常称该图形为“点圆”.应用点圆可简洁、巧妙地解决与直线和圆有关的问题.1.预备结论①设两个相交圆的 In the plane rectangular coordinate system, the equation with a circle centered on (a,b) and r is a radius is (xa)2+(yb)2=r2. If r=0, the above standard equation becomes (xa) 2+(yb)2=0. The graph represented by this formula is an isolated point C(a,b) in the plane rectangular coordinate system. It is often called the “point circle”. The application of the circle can be concisely and skillfully solved. Issues related to lines and circles 1. Preliminary conclusions 1 Set two intersecting circles