TIẾT 12 :TRUNG ĐIỂM CỦA ĐOẠN THẲNG

BGGADT
BGGADT
TUAN ANH-THCS KIEU PHU
TUAN ANH-THCS KIEU PHU
1
1
ngêi so¹n gi¶ng: nguyÔn m¹nh hïng
ngêi so¹n gi¶ng: nguyÔn m¹nh hïng
Tæ TRëng tæ to¸n lÝ
Tæ TRëng tæ to¸n lÝ
BGGADT TUAN ANH-THCS K
IEU PHU
2
KIÓM TRA BµI Cò

a
b
omo

m

BGGADT TUAN ANH-THCS K
IEU PHU
3
TIÕT11
TIÕT11
:TRUNG §IÓM CñA
:TRUNG §IÓM CñA
®o¹n th¼ng
®o¹n th¼ng
1.Trung ®iÓm cña ®o¹n th¼ng :

a.®Þnh nghÜatrung ®iÓm m ab!
"#$a,b %a,b&
'!" ab
Ma+mb=ab
Ma=mb
(
)&*" ab+,-.!"
chÝnh gi÷a ab
a
b
m
Minh ho¹ trung ®iÓm
BGGADT TUAN ANH-THCS K
IEU PHU
4
TRUNG §IÓM CñA ®o¹n th¼ng
TRUNG §IÓM CñA ®o¹n th¼ng
*/0/1i !" mn :
m
n
i
m
n
i
m
n
i
h1
h2
h3

BGGADT TUAN ANH-THCS K
IEU PHU
5
TRUNG §IÓM CñA ®o¹n th¼ng
TRUNG §IÓM CñA ®o¹n th¼ng
2.C¸ch vÏ trung ®iÓm cña ®o¹n th¼ng
®2b (34
a
b
m
5n6" ab ?
&7®
®8abam(ab
94/m!" ab
)&7g:;:<
a
b
BGGADT TUAN ANH-THCS K
IEU PHU
6
A
B

c.C¸ch 3d=;
'
BGGADT TUAN ANH-THCS K
IEU PHU
7
TRUNG §IÓM CñA ®o¹n th¼ng
TRUNG §IÓM CñA ®o¹n th¼ng

3.LuyÖn tËp :
>®%?0<0 @0
®"A!" abB
C. ia=ib
)C&Ia+ib=ab
C&ia+ib=abia=ib
C.Ia=ib=1/2 ab
s
s
®
®
BGGADT TUAN ANH-THCS K
IEU PHU
8
2.Bµi 2cabDc!"#$a,b
'!" acDn !" bc.tEmn
m
n
c
a
b
F,GH
'!" ac
( )
1
1
2
CM AC
=
!" Bc

( )
1
2
2
CN BC
=
*I94941
( )
1 1
.10 5
2 2
CM CN AC CB cm
+ = + = =
J
Dù §O¸N VÒ §é DµI MN
BGGADT TUAN ANH-THCS K
IEU PHU
9
4. Hø¬ng dÉn häc bµi
K,-BL" 
7" 
7MNB
O)N;sgk Dsbt
BGGADT TUAN ANH-THCS K
IEU PHU
10