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1、 12 ,12.2 SSS, ,1. , ,2. ,2. ,.,.,3. ,2. , , ,2. ,3. ,4. , ,: ,4cm,5cm,7cm.,1. AB=4cm,2. AB5cm 7cm C,3. ABAC,ABC.,A,B,C,SSS, ,. (SSS),?, A = _ B = _ C = _, ABC ADCSSS,1 AB=ADBC=CD ABC ADC,AC,AC ( ),AB=AD ( ) BC=DC ( ),ABCADC,=, ABC ADC, ,裺,裺,2 ABCAB=AC ADABCD. ABDACD.,A,B,C,D,(1),(2)BAD =
2、CAD.,21ABDACD BAD= CAD. ,AOB AOBAOB=AOB,O,A,B,C,D,O,A,B,C,D,1OOAOBCD 2OAOOCOAC 3CCD2D 4D仭OB AOB伴,. AOBOAOBOM=ONMN. COCAOB., P8,AC=FEBC=DEAD B FAD=FB. ABC FDEAC=FEBC=DE,ABC FDE AB=DF,AD=FB AD+DB=FB+DB AB=FD,AC=FEBC=DEAD B FAD=FB. ABC FDEAC=FEBC=DE,AB=ACAE=ADBD=CEAEB ADC,BD=CE BD-ED=CE-ED BE=CD,ACE,AD
3、BADC,BC=ED,ACD,(1),(2)裺,2.裺,1. SSS, 12 ,12.2 SAS, ,SSS,ABC DEF, ABC DEFSSS,1,SSS,𣿼.,(2) ,(1) ,(3) ,(4) ,:,SSS,!,?, , A,ABAC, ,:, ABCABC ,: 1. DAE= A,2.ADAB=AB, AEAC=AC;,3. BC.,A,C,B,A,E,C,D,B,2,ABCDEF,ABCDEFSAS,(SAS),F,E,D,C,B,A,1.,AOBDOC A0=DO,=,BO=CO, AOBDOC( ).,AOB,DOC,SAS,A=A,=
4、,A,D,C,B,E,AECADB ( ).,2.AECADB,AB,AC,AD,AE,SAS,SASA,?,AC=10cm,BC=8cm, A=45 .,ABC?,SSA, ABCABC,SAS), ,SSS, SAS,鲣鲣,SAS.,1ABA BCACDCD =CABC ECE =CBEDDEAB,ABC DEC , ABC DECSAS AB =DE ,:ABCBAD,AC=BD CAB=DBA AB=BA,ABCBADSAS,(),(),(),BC=AD (,2AC=BDCAB= DBABC=AD,1: AC=BD,BC=AD :C=D,2: AC=BD,BC=AD :A=B,A,D,
5、C,B,ABACDCDB,: ABCABD,AB=AB,(), BAC= BAD=90,AC=AD,(),ABCABDSAS,BC=BD (, ,2EFACAD/BCAD=CBAE=CF 1AFDCEB,A=C, ,AD / BC,AD = CB,AE = CF,AF = CE,AD/BC, A=C,AE=CF,AFDCEB,AD=CB,A=C,AF=CE,AFDCEBSAS,AE+EF=CF+EF AF=CE,(,(,(,1,SAS,2,SSSSAS, 12 ,12.2 ASAAAS, , 1. 2., , ,49/27,A,B,D,A,B,C,SSA,S
6、SS,𣿼.,(2) ,(1) ,(3) ,(4) ,:,SSS,!,?,SAS, ,A,B,C,A,B,C,1,2,1 ABAB,2 BCA,ABCA B C A B =AB , A = A B = B,:2(ASA).,A B C ABC ,: 1. A B =AB,2.A B DA B = A ,EB A = B, A DB EC,A,E,D,C,B,?,:ABCA B C ,A=A AB=A B,ABCABCASA,A,C,B,B=B,(ASA).,1 AB=AC,B=C,1ABE ACD2AD =AE,: 1ABEACD B=C AB=AC A= A ABE ACD A
7、SA,2,2ABE ACDASA AE =AD,? ,?,(2),(1),C,B,E,A,D,(2) ,(2),İ3 飬,ABCDEF,A D, BE, BCEF, ABCDEF,A +B +C1800, D +E +F =1800, A D, BE, CF, ABCDEF, BE, BCEF, CF, ABC DEF ASA,:,AAS,2.1=2C=D AC=AD,ASA,AAS,ASA,仰,ABDEACDFBE=CFABCDEF, BE=CF(),BC=EF(),B=E,ABCDEF,BC=EF,C=F,ABCDEFASA, ABDE ACDF (), B=DEF ,
8、ACB=F, DAB =EAC DAC =EAB. AEBEADDC D =E =90. ADC AEB ,AEBEADDCCD =BEDAB =EACAB =AC, ADC AEBAAS AC =AB, ,: B=DEF, BC=EF, :ABC DEF (1)SAS (2)ASA (3)SSS ;,ACB= DEF,AB=DE,AB=DEAC=DF,(4)AAS ,A= D,1 (SSS),3 (ASA),4 (AAS),2 (SAS),16ABCACB90ACBCMNCADMNDBEMNE. (1)MNCDEADBE (2)MNCDEADBE (3)MNCDEADBE,67/27,(1)
9、 .,ASA.,(2) .,AAS.,3 , 12 ,12.2 HL,HL HL, ,1 ,SSS,ASA,AAS,SAS,3AB BEBDE BEE,2Rt ABC ,BC,AC,AB,1 A= DAB=DE ABC DEF ,ASA,2 A= DBC=EF ABC DEF ,AAS,3AB=DEBC=EF ABC DEF ,SAS,4AB=DEBC=EFAC=DF ABC DEF ,SSS,72,ABC C =90_,ABCRtABC,AC,BC,AB, Rt,.,1,. (AAS),. (ASA)(AAS),
10、 ,.,ac(ac)RtABC,C= CB=aAB=c., MCN=90;, CMCB=a;, B,CCNA;, AB., ABC, ,HL,RtABCRtABC,HL,BC=BC,HL,HL,1,2, ACBCBDAD C =D =90 RtABC RtBAD AB =BA AC =BD RtABC RtBADHL BC =AD,HL, ACBCBDADAC =BD BC =AD,𣺡ABC +DFE =90,2 AC DF ABC DFE ,ACABDEDF CAB FDE . RtABC RtDEF , RtABC RtDEFHL, ABC =DEF DEF +DFE =9
11、0 ABC +DFE =90, ABC BDCD DEAB DFACEFDEDF (1)BEDCFD,(2)ABC,(2) ,BEDCFD B=C AB=AC,ABCDEF, APDQ,AB=DE,AP=DQ, BAC=EDF, ABCDEF,A,B,C,P,D,E,F,Q,BAC=EDF, AB=DE,B=E, ABCDEF,RtABPRtDEQ,AB=DE,AP=DQ,APDQABCDEF APB=DQE=90 RtABPRtDEQ,AB=DE,AP=DQ,RtABPRtDEQ (HL) B=E ABCDEF,BAC=EDF AB=DE B=E,ABCDEF (ASA),ABCDEF,AP
12、DQ, AB=DE,AP=DQ,BAC=EDF, ABCDEF,ACBCBDAD. 1CAB= DBABC=AD. 2AC=BDBC=AD., 1ACBC,BDAD D=C=90. ABCBAD D=C CAB= DBA AB=BA ABCBAD(AAS). BC=AD.,2ACBC,BDAD D=C=90. RtABCRtBAD AB=BA AC=BD RtABCRtBAD(HL). BC=AD.,AEABBCAB EAD=ABC=90. RtEADRtABC ED=AC EA=AB RtEADRtABC (HL). AED=BAC. EAF+BAC=90 EAF+AED=90 EFA=90 EDAC.,AEABBCABAEABEDAC EDAC,ACBDEAEBCABDBACDEABAC+BD, 1 2,SAS, ASA , AAS , SSS , SAS , ASA , AAS , HL , SSS ,
