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证明圆的切线有两种方法:定义法和定理法.证明圆的切线要视情况选用直线和圆相切的证明法.1.定义法:直线与圆的位置关系可以通过比较圆心到直线的距离d与圆半径r的大小关系来判别,其中,当d=r时,直线与圆相切.当直线和圆的公共点没有明确而需证明直线和圆相切时,可过圆心作直线的垂线,再证圆心到直线的距离等于半径,简称“作垂直,证半径”(或“无点作垂线,证相等”).用定义证明直线和圆
Prove the tangent of the circle there are two ways: the definition of law and theorem. Prove the tangent of the circle, as the case may choose to prove the line and the tangent of the law.1.Definition method: the relationship between the position of the line and the circle can be by comparing the center to the line Distance d and the radius of the radius r to determine the relationship, which, when d = r, the line tangent to the circle.When the straight line and the circle of public point is not clear and need to prove that the straight line and the circle tangent, the center of the circle can be used as a straight line Of the vertical line, then the center of the circle to the distance is equal to the radius of the radius, referred to as “vertical, card radius ” (or “no point for vertical, card ”)