内容正文:
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$TnmL&Yl($'*&
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2.
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.
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1.
8S
,
5△ABC7,AC⊥BC,AE3∠BAC&$Tnm,DE⊥AB,AB=
7cm,AC=3cm,
C
BD
&F3
( )
A.1cm B.2cm C.3cm D.4cm
1
]S
2
]S
3
]S
2.
8S
,AD
3△ABC7∠BAC&$Tnm,DE⊥AB0Y E,S△ABC=7,
DE=2,AB=4,
C
AC
&F3
( )
A.6 B.5 C.4 D.3
3.
8S
,BD
3△ABC&$Tnm,DE⊥AB,e3Y E,△ABC&U3
70,AB=16,BC=12,
C
DE= .
4.
8S
,
Y
O
36m
BE
L&4Y
,∠AOE=36°,OCTn∠AOB,ODTn
∠BOC,h∠AOD&QR.
4
]S
7
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5.
8S
,
6m
AB,CD
20Y
O,OE
3∠AOC&$Tnm,∠DOE=
5∠AOE,h∠BOD&QR.
5
]S
#
45
2
67/KLH1EAAB
6.
8S
,
[\△ABC,h4Y P,cY P∠A'*&2!,. PA=
PB,
iJKY
P
&J&3
( )
6
]S
A.
Y
P
∠A,∠B'$Tnm&Y
B.
Y
P
AC,AB
'*L&M&Y
C.
Y
P
∠A&$TnmNAB&6Tnm&Y
D.
Y
P
AC,AB
'*&6Tnm&Y
7.
8S
,
[\
CE⊥AB,BF⊥AC,CENBF20YD,.BD=CD.hy:Y
D
5∠BAC&TnmL.
7
]S
8
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9
L(45+,
1.A 2.C 3.30°
4.
O
:
ÑÒ
AE,
∵DE
3
AB
&7m
,
∴BE=AE,
∴∠B=∠EAB=15°,
∴∠AEC=30°.
∵∠C=90°,
∴AC=12AE=
1
2BE=2.5.
4
]AS
5.
y
:∵AM=BM,AN=BN,
∴
Y
M,N
,5m
AB
&6T
nmL
.
∵
'YJK4f6m
,
∴
6m
MN
3m
AB
&6T
nm
.
6.
y
:∵AD
3
BC
*L&M
,
∴AD⊥BC.
u
∵BD=DE,
∴AD
>5&6m3m
BE
&
6Tnm
,
∴AB=AE,∴AB+BD=AE+DE.
u
∵AB+BD=DC,
∴DC=AE+DE,
∴DE+EC=AE+DE,
∴EC=AE,
∴
Y
E
5m
AC
&6TnmL
.
4.
/KLH
1
L(ø±)*
1.
2!
2.
2!
9
L(45+,
1.D 2.D 3.5
4.
O
:∵∠AOE=36°,
∴∠AOB=180°-∠AOE=144°.
∵OC
Tn∠AOB,
∴∠AOC=∠BOC=12∠AOB=72°.
∵OD
Tn∠BOC,
∴∠COD=∠BOD=12∠BOC=36°,
∴∠AOD=∠AOC+∠COD
=72°+36°=108°.
5.
O
:∵OE
3∠AOC&$Tnm,
∴∠AOE=∠COE.
∵∠DOE=5∠AOE,
∴∠DOE=5∠COE.
∵∠DOE+∠COE=180°,
∴∠COE=16×180°=30°,
∴∠AOC=∠AOE+∠COE=60°,
∴∠BOD=∠AOC=60°.
6.C
7.
y
:
5△BDE△CDF7,
∵
∠BED=∠CFD=90°,
∠BDE=∠CDF,
BD=CD
{
,
∴△BDE≌△CDF(AAS),
∴DE=DF.
u
∵CE⊥AB,BF⊥AC,
∴
Y
D
5∠BAC&TnmL.
67