怎样正确理解直线和圆的三种位置关系,并初步掌握直线和圆的位置关系的性质与判定,且能够灵活运用,解决一些实际问题?关键是能够用运动变化的观点看待切线,了解切线是一种极限位置.并正确掌握圆的切线的判定定理和性质定理,从图形对称性的角度理解切线长定理,进一步培养自己的“图感”和体会数学中的分类方法和“化归”思想. How to correctly understand the relationship between the three positions of a line and a circle, and to initially grasp the nature and determination of the positional relationship between a line and a circle, and to be able to flexibly use it to solve some practical problems? The key is to be able to treat the tangent from the viewpoint of motion change, and understand that the tangent is An extreme position. Correctly determine the theorem and property theorem of the tangent of the circle, understand the tangent length theorem from the perspective of the symmetry of the graph, further develop its own “graphic sense” and the classification method and the “reification” in the understanding mathematics. Return "Thoughts.