《初中数学人教版八年级上册12.2 三角形全等的判定 优质课件》由会员分享，可在线阅读，更多相关《初中数学人教版八年级上册12.2 三角形全等的判定 优质课件（127页珍藏版）》请在金锄头文库上搜索。
1、12.2 , ,3. ,1. .,2. .,1. ,.,2. ,.,3.ABC DEF.,AB=DE, CA=FD, BC=EF, A= D, B=E, C= F,ABCDEF ?,3cm,3cm,45,45,:.,.,3cm4cm ,4cm,4cm,3cm,3cm,:.,4cm,30:,4cm,4cm,30,30,:.,3045,:.,180., .,., ,.,3060 90 ,.,3cm4cm6cm .,ABCABC,AB= AB ,BC =BC, A C =AC.ABCABC,A ,B,C, 1BC=BC 2B,CAB,ACA 3AB, A C.,. SSS,ABC DEF, ABC
2、DEFSSS.,1 AB =AC AD ABCD1ABD ACD,AD,AB=AC,BD=CD,DBC, D BC BD =DC ABD ACD , ABD ACD SSS ,(2)BAD = CAD.,1ABDACD BAD= CAD. ,.,裺,1. , CBFAB =DC,AC=DF. :ABC DCF.,ABC DCF,AB = DC, ABC DCF,(),(),AC = DF,BC = CF,CBF,BC=CF.,(),(SSS).,2 ABACADAEBDCE. BACDAE.,BACDAE BADCAEABDACEBADCAE., ABD ACE ABAC ADAE BDCE
3、ABD ACE(SSS) BADCAE. BADDACCAEDAC BACDAE.,2. AB=ADBC=DC ABCADC,A,B,C,D,AC=AC ( ),AB=AD ( ) BC=DC ( ), ABC ADCSSS,ABCADC, , , BAC=DAC ACBAD.,ACBAD,AOB AOB=AOB,3 ,O,D,B,C,A,O,C,A,B,D , 1O OA OB CD 2OAOOC OAC 3CCD 2 D 4DOBAOB=AOB,AOBAOB=AOB,1.EF=BCDF=ACDA=EBF=C,DA=BEDE=AB ABCDEF AC=DF BC=EF ABCDEFSSSC=
4、F,AB=DE,2.ADCBAD=BCAE=BFCE=DFAEBF,AD=BCAC=BD ACEBDF ACEBDFSSS A=B AEBF.,AC=BD AE=BF CE=DF,1. DFBCAB=CEAF=DE ABFECD _ (.,BF=CD,2.ABCDADBC, ABCCDB ABCCDA ABD CDB BADC. ( ) A . 1 B. 2 C. 3 D. 4,C,1. AB=AEAC=ADBD=CE ABC AED.,BD=CE,BDCD=CECD .,BC=ED .,=,=,ABCADE,AC=AD AB=AE BC=ED,ABCAEDSSS.,2. AOBAOBAOB=
5、AOB 11OOAOBCD 22OAOOCOAC 3CCD2D 4DOBAOB=AOB 裬 AOB=AOB,1,2,OD=OC=OD=OCCD=CD OCDOCD OCDOCDSSS COD=COD AOB=AOB,OC=OC OD= O D CD= C D,3. ,ADBC,ACBD.:CD .(: AB),AB,ABDBAC(SSS),AD=BC BD=AC AB=BA,ABDBAC,D=C.,ABACBDCDBHCH ,ABDACD(SSS),ABHACH(SSS),BDHCDH(SSS), SSS), ,1. . 2. .,:AB,A,B,A,B,C,E,D,ABC,ACDCD=CA,
6、BCECE=CB,ED,DEAB.,3. SSA,1. SAS.,2. SAS,1. 1 SSS.,3:,SSS,ABCABABACACAA . ABCABC,?, 1DAE=A 2ADAB=AB,AEAC=AC 3BC ., A B C ABC ,ABC DEF,ABC DEFSAS, . SAS ,1 AB=CB ABD= CBD ABD CBD ,:, ABD CBD.,AB=CB(),ABD= CBD(),BD=BD(),ABD CBD,AB=CB(),ABD= CBD(), ABDCBD ( SAS).,BD=BD(),1.:, AB=DB,CB=EB,12:A=D.,: 12()
7、1+DBC 2+ DBC() ABCDBE. ABCDBE, ABDB() ABCDBE() CBEB() ABCDBESAS. A=D().,2 ABABCACDCDCABCECECBDEDEAB?,A,ABC DEC ,ABC DECSAS AB =DE .,2. ABACD.CDB,. BADBAC BD = BC.,𣬰ABC.ABD.,B,A,C,D,ABCABDAB=AB ,AC=AD, B=B,ABCABD.,SSA,ABC ABDA =A =30 AB =AB=5 cm BC =BD =3 cm ,A,B,M,C,D,3 ABCDEF(),AAB
8、DEBEBCEF BABDEADACDF CBCEFBEACDF DBCEFCFACDF,ABCDEFCC.,C,3ABCDABCDEFBDBEDF ( ) A1 B2 C3 D4,C,C,1.AB=ADAC=AEBAE=DAC C=E,BAE=DACBAECAE=DACCAE BAC=DAEABCADE ABCADESASC=E,AB=AD BAC=DAE AC=AE,2.ACBDEAE=DEBE=CE 1ABEDCE 2AB=5CD,1AEBDEC AE=DE AEB=DEC BE=EC AEBDECSAS 2AEBDECAB=CD AB=5CD=5,1.,2.AB=DBBC=BEABED
9、BC ( ) A.AD B.EC C.A=C D.ABDEBC,D,ACBAD BAC=DAC ABCADC ABCADCSAS,AD=AB,BAC=DAC,AC=AC,(,(,(,3.ACBAD, AB=AD ABCADC,AB=AC, BD=CDEAD. BE=CE., BAD=CAD,ABDACD, BE=CE.,ABEACE,ABDACDSSS.,ABEACESAS.,CA=CB , AD=BD, MNCACBDM=DN.,ABDCBD,:,ACDBCDSSS,CD,A=B,MNCACB, AM=BN,AMDBND,AMDBNDSAS,DM=DN., SAS),1. 2., ,岻,1.
10、 ASAAAS,2. ASA AAS,ABCA B C A B =AB A =A B =B ().A B C ABC,A,B,C,E,D, 1AB=AB; 2ABDAB =AEBA =BADBEC., (ASA.,1 ABCDCBACB DBC ABCDCB,ABCDCB( BCCB ACBDBC,ABCDCB,ABCDCBASA .,1. ECBFBECFABDEACBF.ABCDEF.,ABDE BDEF BECF BCEF. ACBF ABCDEFASA,2 DABEACAB=AC, B=C,AD=AE.,ACDABEAD=AE.,ACDABE,A=A AC=AB C=B , ACDAB
11、EASA,AD=AE.,2. AD=AE,B=CBECD,:ABEACD B=C A= A AE=AD ABE ACDAAS BE=CD ,BE =CD,6045453cm?,11,.AAS.,3 ABCDEFADB EBC=EF. ABCDEF,ABCA+B+C180.,ABCDEFASA .,BE BCEF CF., C180AB., F180DE., ADB E, CF.,ABCDEF,4 ABCBAC90ABACmABDmCEmDE. (1)BDAAEC,(1)BDmCEmADBCEA90 ABDBAD90. ABAC BADCAE90 ABDCAE. BDAAEC,ADB=CEA=9
12、0 ABDCAE, ABAC,BDAAEC(AAS).,4 ABCBAC90ABACmABDmCEmDE. (2)DEBDCE.,BDAEADCE DEDAAEBDCE.,BDAAEC,3.ADABCCFADFBEADADE.BECF.,ADABC BDCD. BEADCFAD BEDCFD90. BEDCFD,BED=CFD 1=2 BD=CD,BEDCFD(AAS)BECF.,AB=ACA B=CASAABEACD AD=AESASABEACD BD=CEAD=AESASABEACD BE=CDSSAABEACD,1.DEABACCDBEOAB=ACABEACD AB=C BAD=AECB
13、D=CEDBE=CD,D,2.1=2B=D CB=CD,1=2 ACB=ACD ABCADC B=D ACB=ACD AC=AC ABCADCAAS CB=CD,1. abcABC A B C D,B,2. ABCABCA44B67C69 A44ACAC A B C D,B,3. ACB=DBCABC=CDB.,BC.,4.ABCADBEFADCBEC_,AC=BC,1. ABBCADDC1=2, AB=AD., ABBCADDC, B=D=90 .,ABCADC, ABCADC (AAS),AB=AD.,2. ,? ,?,𣺴1.,ABC ABC ADA D ABC ABC.A
14、D AD 仰.,ABC ABC AB=AB ABD=ABD.ADBCADBC ADB=ADB.ABDABD ADB=ADBABD=ABD AB=ABABDABD.AD=AD.,., , ASA),.,(1),SAS.,ASA,AAS.,.,2?,.,2. .,1. .,SSS,SAS,ASA,AAS, .,HL,RtABCC =90_.,AC,BC,AB,A,B,C,B,C,1.,2.,3.,A,AC=DFBC=EFB=EABCDEF SSA., B=E=90 AC=DFBC=EF ABCDEF,RtABC C=90.RtA B C C=90 BC=BC A B =AB RtAB C RtAB
15、C,1M C N=90.,2CMBC=BC.,N,B,3BABCNA.,N,B,A,4AB.,N,B,A, HL.,RtABCRt ABC ,RtABC Rt ABC (HL)., 1 2 3 4 5 ,HL,AASASA,SAS,AAS,AAS,1 ACBC BDAD ACBD. BCAD., ACBC BDAD CD ., RtABC RtBAD , RtABCRtBAD (HL). BCAD.,HL, ACB =ADB=90 ABC BAD. 1 2 3 4 ,AD=BC, DAB= CBA,BD=AC, DBA= CAB,HL,HL,AAS,AAS,ACBDP ACBCBDADCD A
16、D=BC. AC=BD.,HL,AC=BD,RtABDRtBAC,ABADCDBC AB=CD ADBC.,HL,ADB=CBD,RtABDRtCDB,ADBC,1.ABCABCBABC90FABEBCAECF.RtABERtCBF.,RtABERtCBFABECBF90 ABCBAECF RtABERtCBF(HL),2 ADAFABCABEADAFACAE. BCBE.,ADAFABCABEADAFACAE RtADCRtAFE(HL) CDEF. ADAFABAB RtABDRtABF(HL) BDBF. BDCDBFEF. BCBE.,HL,2.AEBCDFBCEFAEDFABDCAC
17、DB.,AEBCDFBC AEBDFC90. RtABERtDCFRtABERtDCF(HL) ABCDCB. ABCDCB ABCDCB(SAS) ACDB,3 ACDFBF,RtABCRtDEF, RtABCRtDEF (HL).,B=DEF ()., DEF+F=90,B+F=90.,3. 12,RtABDRtACD(HL) BD=CD,BD=CD ADB=ADC=90 RtABDRtACD, AB=AC AD=AD,1.A=D=90AC=DBACDBO OB=OC,RtABCRtDCB = = RtABCRtDCBHL OBC=OCB BO=CO,DEABDFBCEF AED=CFD=
18、90 DACAD=DC RtADERtCDF = = RtADERtCDF A=CBA=BCAB=AC AB=BC=AC ABC,2.ABCAB=ACDACDEABDFBCEFDE=DFABC,D,1. A. B. C. D.,3.ABCAB=ACADADBADC .,HL,A,2. ABCADBCDCEAB E ADCEHEHEB3AE4 CH A1 B2 C3 D4,4. ABCBDACCE ABBD=CE.EBCDCB., BDACCEAB BEC=BDC=90 ., RtEBC RtDCB , RtEBCRtDCB (HL).,AB=CD, BFAC,DEAC, AE=CF.BF=DE.,: BFAC,DEAC, BFA=DEC=90 . AE=CF AE+EF=CF+EF. AF=CE. RtABFRtCDE, RtABFRtCDE(HL).,BF=DE.,ABCC90AC10cmBC5cmPQABPQACAACAQPACABCAPQ,(2)PCAPAC. RtABCRtQPA PQABAPAC RtQAPRtBCA(HL) APAC10cm AP5cm10cmABCAPQ,(1)PAPBC CQAP90. RtABCRtQPA PQABAPBC RtABCRtQPA(HL) APBC5cm,., ,
