志鸿同步测控设计2015-2016学年北师大版数学选修4-1全册课件 1.2.2 圆的切线的判定和性质

1、-1-2 2.2 2圆的切线的判定和性质-2-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航1.复习、回顾直线与圆的位置关系及其判断方法.2.理解并掌握切线的判定定理、性质定理及推论.3.理解切线长定理.-3-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456-4-2.2圆的切线的判定和

2、性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456-5-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456-6-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG

3、目标导航123456-7-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456-8-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456-9-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANL

4、I TOUXI典例透析MUBIAODAOHANG目标导航123456-10-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航124356-11-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航124356【做一做4】 直线l与O相切,P是l上任一点,当OPl时,则().A.点P不在O上B.点P在O上

5、C.点P不可能是切点D.OP大于O的半径解析:由于OPl,则P是l与O的切点,则点P在O上.答案:B-12-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456-13-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456【做一做5】 直线l与O相切于点P,在经过点P的所有直线中,经过

6、点O的直线有().A.1条B.2条C.3条D.无数条解析:过点P且垂直于l的直线仅有1条,此时圆心O在该垂线上,故选A.答案:A-14-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456-15-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航123456-16-2.2圆的切线的判定和性质Z

7、HISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航1.与圆的切线有关的知识剖析:(1)切线和圆只有一个公共点;(2)切线和圆心的距离等于圆的半径;(3)切线垂直于过切点的半径;(4)经过圆心且垂直于切线的直线必过切点;(5)经过切点且垂直于切线的直线必过圆心.-17-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航2.判定切线的

8、方法剖析:判定切线通常有三种方法:(1)定义法:和圆有唯一一个公共点的直线是圆的切线;(2)距离法:到圆心的距离等于半径的直线是圆的切线;(3)定理法:过半径外端且和该半径垂直的直线是圆的切线.“过半径外端,垂直于这条半径的直线是圆的切线”是“到圆心的距离等于半径的直线是圆的切线”的具体化.在使用时要根据题目的具体要求选取合适的方法.若已知要证的切线经过圆上一点,则需把这点与圆心相连,证明这条直线与此半径垂直,即用定理法;若不能确定要证明的切线与圆有公共点,则需先向这条直线作垂线,再证明此垂线段是圆的半径,即用距离法证明.通常不用定义法证明.-18-2.2圆的切线的判定和性质ZHISHI SH

9、ULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-19-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-20-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导

10、航题型一题型二题型三-21-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-22-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-23-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN

11、随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三证明:如图所示,连接OE.OA=OE,OEA=OAE.又AE平分BAF,OAE=EAF.OEA=EAF.OEAD.ADCD,OECD.CD与O相切于点E.即CD是O的切线.-24-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-25-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUIT

12、ANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-26-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-27-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-28-2.2圆的切线的判定和性质ZHI

13、SHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-29-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航题型一题型二题型三-30-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOH

14、ANG目标导航1 2 3 4 51已知AB是O的切线,在下列给出的条件中,能判定ABCD的是(). A.AB与O相切于直线CD上的点CB.CD经过圆心OC.CD是直线D.AB与O相切于点C,CD过圆心O-31-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航1 2 3 4 5-32-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析M

15、UBIAODAOHANG目标导航1 2 3 4 5-33-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航1 2 3 4 5-34-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航1 2 3 4 5-35-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚

16、焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航1 2 3 4 5解析:DA,DC为O的切线,DA=DC.同理EB=EC.PDE的周长=PD+PE+DE=(PD+DC)+(PE+CE)=(PD+DA)+(PE+EB)=PA+PB=7+7=14.答案:C-36-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航1 2 3 4 5-37-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO重难聚焦SUITANGYANLIAN随堂演练DIANLI TOUXI典例透析MUBIAODAOHANG目标导航1 2 3 4 5解析:如图所示,连接OD.CD与O相切,ODDC.OA=OD,A=ODA=25.COD为AOD的外角,COD=50,C=40.答案:40-38-2.2圆的切线的判定和性质ZHISHI SHULI知识梳理ZHONGNAN JVJIAO