Tiết 40: Tính chất tia phân giác

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C
A
B
D
E
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DB
DC
EB
AC
)!
¸*+,
-.(
ˆ
ˆ
⇒CAE = AEB BE//AC
DB EB
=
DC AC
a
a//BC
B
A
C
C'
B'
a
a//BC

B
C
C'
B'
A
a
a//BC
B
C
C'
B'
A
AB'
AB
=
AC'
AC
=
B'C'
BC
0
ˆ
A 100=
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AB
AC

DB
DC
2
3
4
6
5
8
1
0
2
3
4
6
5
8
1
0
1
0
2
3
4
6
5
8
1
0
A
x

.
6 C
2
3
4
6
5
1
0
.
5
.
2,5
D
B
3
DB
DC
AB
AC
= =
2
1
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
C
A
B
D
E
AB = EB
DB
DC
AB
AC
=
=>
DB
DC
EB
AC
=
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A
1
= A
2

=,3
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(2)
DB
DC
BE
AC
=
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DB
DC
AB
AC
=
A
B C
D
E
1
2
A
CB

D
F
DB
DC
AB
FC
=
AC = FC
=>
DB
DC
AB
AC
=
C
A
B
D
3,5
7,5
x y
7 . 5
U4VE.(
x
5
7
15
= => x =
15
=> x =

7
3
1
3
= 2
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y
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b)
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AB
AC
= 
x
y
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7,5
=
7
15
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D
E
F

H
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8Y
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8N
8Y
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. ($/0"&1"2+"2+"3'4*5&%&6'7%
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=
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D C AC
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⇒ =
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(1)
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AB D B
AC D C
A
B
C
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D’
2
1
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AB
AC

=
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=
A
B
C
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2
1
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A
C
D
E
F
DB
DC
AB
AC
=
EC
EA
BC
BA
=
FA
FB
CA

CB
=
D
E
F
H
3
5
8,5
x
N
Y
8N
8Y
=
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
3
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5
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18
82
1a
a2
=
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1N
N
1a
a
=
1O
2O
O
a24a
18
82
4
2
1
A
B C
M
D
E
2@`VR,H(
(D&:+"EFG&:HC
*I2J&K)&LM&

#E&'()"'**,("-*
NO&(*-<&L*
AB DB
AC DC
=
4,5 3,5
7, 2 x
⇔ =
7, 2.3,5
4,5
5,6
x
x
⇔ =
⇔ =
C
D
x
4,5 7,2
3,5
A
B
PEF(
P
M
Q
N
6,2 8,7
x
12,5

2@`VR,H(
QD&:+"E$2( G&:HBC&= C*I2J&K
)&LM&
=> 6,2x = 8,7(12,5 – x)
=> 6,2x = 8,7.12,5 – 8,7x
=> 6,2x + 8,7x = 8,7.12,5
=> 14,9x = 8,7.12,5
QM
QN
PM
PN
=
EVX
X
6,2
8,7
=
=> x =
8,7.12,5
14,9
≈
7,3
.
bL<,b
4S

Híng dÉn vÒ nhµ
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c3%`
19





A
B
CD
E
F
B@i 18: (SBT/69)
HDVN
L"G':R"
. . 1
DB EC FA
DC EA FB
=
(1)
DB
DC
=
(2)
EC
EA
=
(3)
FA

FB
=
N)C3'C*,(4S3'(