内容正文:
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2.D
V²
:
o({#¥ïùÜ
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3.C
V²
:
24{#4g.
、
*.*-.'24{
#
.
4.A
V²
:
ÒNo(24{#çeD
NP=BC.
p7
BC=2,
Cf
NP=2.
5.C
V²
:
_*¬2E&sb{
,
£bs#~17
2;
äZ
E{&sb{
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0bs#~17
3,
f¨
C.
6.D
V²
:
,
p7 ∠A+∠B+∠C=180°,
∠A=∠C-∠B,Cf2∠C=180°,Cf∠C=
90°,
Cf△ABC&424{,f¨D.
7.C
V²
:
pq~beD △ABE≌ △DCF,
△EBF≌△FCE,△ABF≌△DCE,f3b.
8.D
V²
:15-10<AB<15+10,
Ì
5<AB<25,
f¨
D.
9.D
V²
:
p7∠1=65°,AD∥BC,Cf∠DEF=65°,
Cf∠DEG=2∠DEF=130°,
Cf∠BGE=∠DEG=130°.
10.C 11.80°
12.6
V²
:
o(24{#|xA(
,
b2A(
.
13.38 14.8
15.15°
V²
:
k△ABC&(24{,
Cf∠B=∠1=60°,¢CD=CG,
∠CGD=∠2=180°-(180°-∠1)2
=∠12,eD ∠1=2∠2,¢ DE=DF, ∠DFE=∠E=
180°-(180°-∠2)
2 =
∠2
2,eD∠2=2∠E,Cf4∠E=60°,C
f∠E=15°.
16.
V
:(1)
,∠ABDÌ7Cv.
(2)
p7∠ABC+∠C+∠A=180°,
Cf ∠ABC =180°-90°-30°
=60°,
p7∠ABD=∠C=30°,
Cf∠DBC=∠ABC-∠ABD=60°-30°=30°,
Cf∠BDC=180°-30°-30°=120°.
17.
V
:
p7
EM
&
AB
#1g.
,
Cf
AM=BM,
Cf∠BAM=∠B,
«ü
,∠NAC=∠C,
qp7∠BAC=115°,
Cf∠B+∠C=180°-∠BAC=180°-115°=65°,
Cf∠BAM+∠CAN=∠B+∠C=65°,
Cf∠MAN=∠BAC-(∠BAM+∠CAN)=115°-65°=50°.
18.
V
:(1)
pq
AD
&△ABC#*.,AE&△ACD#*.,DE=2,5
CE=DE=2,BD=DC=2DE=4,BE=BD+DE=4+2=6,
BC=2BD=8.
(2)
pq△ACE#|x74,△ACD,△ABCw△ACE(,£DC=
2CE,BC=2CD,
f
S△ACD =2S△ACE =8,S△ABC =2S△ACD =16.
19.
V
:(1)
_{D
:AC=BC,∠ACB=90°,AD⊥DE,BE⊥DE,
Cf∠ADC=∠CEB=90°,
Cf∠ACD+∠ECB=90°,∠ACD+∠DAC=90°,
Cf∠ECB=∠DAC.
'△ADC△CEB*,
p7∠ADC=∠CEB,∠DAC=∠ECB,AC=BC,
Cf△ADC≌△CEB(AAS).
(2)
_{D
:AD=2×3=6(cm),BE=7×2=14(cm),
p7
△ADC≌△CEB,CfCE=AD=6cm,CD=BE=14cm,Cf
DE=CD+CE=20cm,
Cf+U89#:;7
20cm.
20.
V
:́
Ú
BO,CO,
p7∠BAC=50°,AOg∠BAC,
Cf∠OAB=∠OAC=25°.
p7
OD
1g
AB,
Cf
AO=BO,
Cf∠OAB=∠ABO=25°,
'(q△ABC*,p7AB=AC,∠BAC=50°,
Cf∠ABC=∠ACB=65°,
Cf∠OBC=65°-25°=40°,
p7
AB=AC,AO
g∠BAC,
Cf
AO
C'.&
BC
#1g.
.
Cf
OB=OC,
Cf∠OBC=∠OCB=40°,
p78
C
÷
EF
°±Ñw8
O
'
,
Cf∠CEF=∠FEO,EO=EC,
Cf∠EOC=∠OCE=40°,
Cf∠CEF=180°-2×40°2 =50°.
21.
V
:
«CU
.(
NÝgO^
)
22.
V
:(1)
_eq
,
b8y
A
A′,B
B′,C
C′.
(2)
,́
Ú
AA′,
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m
&.>
AA′
#1
g.
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(3)
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jz.>
AC
w
A′C′,
}#08
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m
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w
A′B′,BC
w
B′C′
#08
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m
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m
b
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£±gÃ
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5}#08
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