志鴻同步測控設(shè)計2015-2016學(xué)年北師大版數(shù)學(xué)選修4-1全冊課件1.2.2圓的切線的判定和性質(zhì)

1、-1-2 2.2 2圓的切線的判定和性質(zhì)-2-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航1.復(fù)習(xí)、回顧直線與圓的位置關(guān)系及其判斷方法.2.理解并掌握切線的判定定理、性質(zhì)定理及推論.3.理解切線長定理.-3-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-4-2.2圓的切線的判定和

2、性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-5-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-6-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG

3、目標導(dǎo)航123456-7-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-8-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-9-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANL

4、I TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-10-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航124356-11-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航124356【做一做4】 直線l與O相切,P是l上任一點,當(dāng)OPl時,則().A.點P不在O上B.點P在O上

5、C.點P不可能是切點D.OP大于O的半徑解析:由于OPl,則P是l與O的切點,則點P在O上.答案:B-12-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-13-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456【做一做5】 直線l與O相切于點P,在經(jīng)過點P的所有直線中,經(jīng)過

6、點O的直線有().A.1條B.2條C.3條D.無數(shù)條解析:過點P且垂直于l的直線僅有1條,此時圓心O在該垂線上,故選A.答案:A-14-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-15-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航123456-16-2.2圓的切線的判定和性質(zhì)Z

7、HISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航1.與圓的切線有關(guān)的知識剖析:(1)切線和圓只有一個公共點;(2)切線和圓心的距離等于圓的半徑;(3)切線垂直于過切點的半徑;(4)經(jīng)過圓心且垂直于切線的直線必過切點;(5)經(jīng)過切點且垂直于切線的直線必過圓心.-17-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航2.判定切線的

8、方法剖析:判定切線通常有三種方法:(1)定義法:和圓有唯一一個公共點的直線是圓的切線;(2)距離法:到圓心的距離等于半徑的直線是圓的切線;(3)定理法:過半徑外端且和該半徑垂直的直線是圓的切線.“過半徑外端,垂直于這條半徑的直線是圓的切線”是“到圓心的距離等于半徑的直線是圓的切線”的具體化.在使用時要根據(jù)題目的具體要求選取合適的方法.若已知要證的切線經(jīng)過圓上一點,則需把這點與圓心相連,證明這條直線與此半徑垂直,即用定理法;若不能確定要證明的切線與圓有公共點,則需先向這條直線作垂線,再證明此垂線段是圓的半徑,即用距離法證明.通常不用定義法證明.-18-2.2圓的切線的判定和性質(zhì)ZHISHI SH

9、ULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-19-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-20-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)

10、航題型一題型二題型三-21-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-22-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-23-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN

11、隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三證明:如圖所示,連接OE.OA=OE,OEA=OAE.又AE平分BAF,OAE=EAF.OEA=EAF.OEAD.ADCD,OECD.CD與O相切于點E.即CD是O的切線.-24-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-25-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUIT

12、ANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-26-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-27-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-28-2.2圓的切線的判定和性質(zhì)ZHI

13、SHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-29-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航題型一題型二題型三-30-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOH

14、ANG目標導(dǎo)航1 2 3 4 51已知AB是O的切線,在下列給出的條件中,能判定ABCD的是(). A.AB與O相切于直線CD上的點CB.CD經(jīng)過圓心OC.CD是直線D.AB與O相切于點C,CD過圓心O-31-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航1 2 3 4 5-32-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析M

15、UBIAODAOHANG目標導(dǎo)航1 2 3 4 5-33-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航1 2 3 4 5-34-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航1 2 3 4 5-35-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚

16、焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航1 2 3 4 5解析:DA,DC為O的切線,DA=DC.同理EB=EC.PDE的周長=PD+PE+DE=(PD+DC)+(PE+CE)=(PD+DA)+(PE+EB)=PA+PB=7+7=14.答案:C-36-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航1 2 3 4 5-37-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO重難聚焦SUITANGYANLIAN隨堂演練DIANLI TOUXI典例透析MUBIAODAOHANG目標導(dǎo)航1 2 3 4 5解析:如圖所示,連接OD.CD與O相切,ODDC.OA=OD,A=ODA=25.COD為AOD的外角,COD=50,C=40.答案:40-38-2.2圓的切線的判定和性質(zhì)ZHISHI SHULI知識梳理ZHONGNAN JVJIAO