参考答案(同步练习册 八年级上册)(福建版)

+
+源自文库
BG-112-::frLABC, :. LABC = 2LGBC,.:RLABC = 2LAED, :. LAED = LGBC,.:R ·: AE // BC, :. LEAF= LC, .:RAE= BC,:• .6AEF (/) .6CBG, :. EF = ffi 8. Cl)·: AB //CD, :. LCMA = LBAM, EBR;/;]f'F7*1tT~:AP -112-::fr LO\.B, :. LCAM =
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DB f'p LCOD = LWB = La,9!tl LCOB = 2La; @f'p LCOA = L/3; @LAOB ~Yr>l<f'FE19J§, ~p LAOB = 2La- L/3. C~Dl!lfJrlR)
iJBt 1 ft-~~J§Jt~rBffl~fJL ft- 1-:ffl~rBffl:ffJ [ff~( sl~)] sl:it 1. f'p~: CDf'FM~ AP;@tEM~ AP ...t{&?j(~Ijj{ AC = a, CD = = b; @~.§tAB ~Yr>J<f'F~.§t, ~p AB= a+ 2b Cl!!~) sl:i\: 2. f'F~:CDf'FM~ OC;@,f&?j(
LAOB=
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~it 2. 00~,icM~ BP ~M~ CQ fflxr,i,~ D, LC 89>'~JfJjgLACE ,!J!UER
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nx;a{]i]tft§jgLBDC,'t~LA a{]~*jg LBDC
~ LA,fll!EB~: ·: BP -112-% LABC,
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-112-::fr
LACE, :. 2LDCE = LA + 2LDBC,.:R LDCE = LDBC+ LBDC, :. LBDC =
~ LA
[&~('(JE~)] 1. B 2. A 3. i!li!li!l 4. f'FB~JfJB9¥-:5t~ s. ~ 6. f'l::00~,0D_l OE, fl!! EB~:·: LAOB LIDC = 180°, .:R OD -112-::fr LAOB, OE -112-::fr LIDC, :. 2LWB 2LIDE = 180°, ep LWB + LIDE = 90°, :. LWE = 90°, :. OD _l OE 7. Cl) f'l::00~
[&t~(i.i'E~)]
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illfit 4 ftBffl~¥Jt((.J:ji;_aift5}~ [ffM( sl~)] ~it 1. ~ ~it 2. f'l::7*:CDf'FM~ BP;®tl:M~ BP _t~}lkBC = b; ®fl:: ~~BC 89*][¥-::fr~MN ;@~,#, B jgOO,C,,,~ a a{J*:1g¥-1:£1!!If5Jll:XMN r,#,A,~~ AB,AC; @.6ABC jgEJr>)<:fpa{]=ft§%. (00~)
(2) ·;
LBAM, :. LCMA = LCAM, .:R LACD = 114°, :. LM4.B = LCAM = LCMA =
(180° - 114°) = 33° (2) ·: CN _lAM,
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:. LCNA = LCNM,.:RLCMA = LCAM, CN = CN,
: • .6ACN (/) .6!vICN
:i11:i11:i11 4. 1tB~~~Ef9¥H¥-:5Hi 5. m7T\:1f AB :i11 E19¥1r¥-:5t~x1[~AC T,~P.9lU PA= PB 6. mlT\d!~AB, BC,:5tJJLl1t~~AB, BC E19 m1r¥-:5t~.IJ!Ll;rt:xAu1Jt:Jild;[9J"~ P 1. :tiam 8. :tiam
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[&~({fE~)] 1.C 2.D 3.(m~Jl'. ,ri~;M)j'.EJ91LR 4.Cl)M~OP,OA (2)A,r89 K,M~ AP, B s. f'F~:CDf'FM~ OP;@tEM~ OP ...t{&?j(~Ijj{OA = a, AB= b; @&foJ~Ijj{ BC= c; @~.§t OC ~Yr>J<f'FEl9~.§t, ~p CC= a+b-c; (00~) 6. t'tlR: PIJ'Gf'FLa, Lr 895fll, ~§tELa, Lr 895fl189P3$f'FL/3 7. t'tlR :7'6f'F-~~.§t BC= b, .pJ.:5tjJ1Jt;,(,~ B, C ~[m,C,,, t;,( a 89*~-*11@W3'.tr,~ A,ji~ AB, AC,9!tl6ABC ~Yr>J<f'FE19~Jlf.=J§% 8. t't7R:7'6f'F~.§t
illfit 3 ~,:t~Bffl.'i'MtBffl.a~((.J:ji;~ [ffM( sl~)] ~it 1. ~ ~it 2. f'l::7*:CDf'FM~AP;®tEM~AP J:~IlitAC = b; ®M ,#, A f'FM~AP a{]*~AT;@tl: AT l:~IlitAB = a,~~ BC;@.6ABC jgEJr>)<:f'Fa{J][JfJ.=::JfJ %. GmOOEJrlR)
[&~({fE~)] 1. C 2. C 3. ~)ll]:j§ 4. 3 5. ,0,ACE ~~)ll=J§%,Jll!EH~: ·; AD f?tLBAC, :. LEAD= LOlD,JZ. ·: CE II AD, :. LEAD= LE, LOlD = LACE, :. LE =LACE,:. AC= AE, :. 6ACE ~~Jlf.=J§% 6. tE~:l226ABC q:t, ·:AB= BC =O\., LA =LB= LC,JZ.AD =BE= CF, :. AB - AD= BC - BE= Ol - CF, ~p DB =Fr= FA,:. ,0,ADF u:> ,0,BED u:> ,0,CFE, :. DF =ED= FE, :. ,0,DEF ~~:lll.=J§% 7. Cl) xf,Jll!EH~:tE~:l226ABC q:t, ·; LABC =LACE= 60°, Jl ·: BD f?t LABC, :. LDBC = 30° ,Jl CD= CF, :. LF= LCDF ,Jl ·: LF+ LCDF = D LACE =60°, :. LF = 30°, :. LDBC = LF, :. BD = DF (2) 1:iJ i;,(fe"BD f?tLABC"~~"BD ~ AC :lll...t.899'1~(~~)" ,Jll!EH~:l& ffl~Jlf .=J§%89" -=~it--"1&~1:iJt;,(ftt'Jj"BD f?tLABC" 8. ~Di!!, ~* AE JU,~ F ,it EF =AB, ji~ DF. tE~:lll ,0,ABC q:t, ·: AB = AC =BC, LA= 60°, Jl ·; CD = AE, :. AD = AF, :. ,0,ADF ~~:lll A B E F .=J§% , :. AD = FD, LF = 60°, :. ,0,ABD u:> ,0,FED, :. DB = DE
BC= a,
f'&J§-%£U~ B, Cjg]]j!Af'FJfJ:5t£U~rLa, Li9,ep-aJf'FiliJ!t = JfJ% illfit 2 ftBfflJfJ(l{Jift:$}~
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mlR :5tf'l::La 89¥-%~ ,1,~J
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PE,JZ.AB =AC,:. PE+PF = a PE = a
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[ff~(sl~)] sl:i\: 1. ·;LACE= 90°, CD l_AB, :. LO\.E + LCEA = 90°, LE4.B+ LAFD = 90°,JZ. ·: AE}Jl-:5t LO\.B, :. LOlE = LE4.B, :. LCEA = LAFD,JZ.LAFD = LCFE, :. LCEA = LCFE, :. CF = CE sl:i\: 2. ·;AB = AC, LA= 108°, :. LABC = LC= 36° ,Jl ·: BD f?t LABC, :. LABD = LDBC = 18°, :. LADE= 180° - 108° - 18° = 54°, LCDB = 180° - 36° - 18° = 126° ,ft BC :lll...t~Ijj{ CE= CD ,J)!tl LCDE = LCED = 72°, :. LEDB = 126°-72° = 54°, :. LADE= LEDB,Jl BD = BD, :. ,0,ABD u:> ,0,EBD, :. BE = AB, :. BC = BE + CE = AB+ CD
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