cho 2 diem M va N nam Cung phia voi A , nam cung phia doi voi B . Diem M nam giua A va B . biet AB =3cm,BN=1cm.chung to rang:
a, bon diem ABMN thang hang
b, diem N la trung diem cua doan MB
c , ve dung tron tam N di qua B va duong tron tam A di qua N , chung cat nhau tai C tinh chu vi tam giac CAN
cho hai diem M va N nam cung phia doi voi A,nam cung phia doi voi B. diem M nam giua Ava B biet Ab =5 cm AM =3cm BN=1cm .CMR BON DIEM A ,B , M,M nam thang hang va diem N la trung diem cua doan thang MB
Cau 5: Trong cac khang dinh sau, khang dinh nao dung, khang dinh nao sai?
1.Ba diem phan biet la ba diem thang hang.
2.Voi ba diem phan biet luon co hai diem nam ve cung phia doi voi diem con lai.
3.Voi ba diem thang hang phan biet luon co hai diem nam khac phia voi diem con lai.
4.Voi ba diem A,B,C thang hang thi diem B luon nam giua hai diem A,C.
5.Co mot va chi mot duong thang di qua hai diem (phan biet) cho truoc.
6.Hai duong thang phan biet thi song song voi nhau.
7.Hai tia chung goc thi cung nam tren mot duong thang.
8.Hai tia chung goc thi doi nhau
9.Neu diem M nam giua diem A,B thi no la trung diem cua doan thang AB.
10.Neu MA=MB thi M la trung diem cua doan thang AB.
11.Neu MA+MB= AB va MA=MB thi M la trung diem cua doan thang AB.
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cho 3 diem A,B,C khong thang hang
a)Ve duong thang AB, doan thang BC,tia AC.Lay dien M tren duong thang AB sao cho B,M nam cung phia so voi diem A
b)Ve tia Ax la tia doi cua tia AC.Lay diem N sao cho A la trung diem cua doan CN(ve tren cung 1 hinh)
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cho cac diem A va B thuoc duong thang a .diem C nam giua A va B .diem D nam giua C va B
a)tim tren duong thang a nam cung phia doi voi diem C diem nam khac phia doi voi diem C
b) tim tren hinh ve cac tia doi nhau goc C ,cac tia trung nhau goc C
c) vi sao diem C nam giua A va D
ve 4 diem A,B,M,N sao cho diem A nam giua M va B , diem N nam giua A va B
a ) hay cho biet diem A nam giua 2 diem nao .
b ) Tim cac diem nam cac phia doi voi A
Ve tren cung mot hinh theo cach dien dat sau :
a)Ve 4 diem A ,B ,C D sao cho C nam giua A, B va 3 diem A, B D ko thang hang . Hay ve va ke ten duong thang (phan biet) di qua tung cap diem .
b) Ve diem E sao cho E va D nam khac phia doi voi A . Ve diem F sao cho C,E,F thang hang va F thuoc duong thang DB
Cho doan thang AB.§iem C cach deu hai diem A,B. Diem D cach deu hai diem A,B(D va C nam khac phia doi voi AB)
a) Chung minh rang: Tia CD la tia phan gia cua goc ACB
b) Ket qua cau a con dung khong neu C,D nam cung phia voi AB?
Bai 1
Cho tam giac nhon ABC , diem M thuoc canh BC , goi D la diem doi xung voi M qua AB , goi E la diem doi xung voi M qua AC. Goi I,K la giao diem cua DE voi AB va AC
a,CMR ; MA la tia fan giac cua goc IMK
b,Tim vi tri cua diem M de DE co do dai nho nhat
Bai 2
Cho hai diem A va B nam cung phia doi voi duong thang d.goi AH , BK la cac duong vuong goc ke tu A , B den d.Goi C la diem bat ki nam giua H va K
a,Ve diem A' doi xung voi A.cmr goc ACH = goc A'CH
b,Gia su goc ACH = goc BKC ,cmr khi do 3 diem A',C,B thang hang
c,Neu cach dung diem C nam giua H va K sao cho goc ACH = goc BKC
SACH CAC DANG TOAN VA PHUONG PHAP GIAI LOP 8
