cho doan thang AB . Cla trung diem cua AB M la diem nam giua B va C , Chung to rang MA - MB = 2MC
Cho doan thang AB va 1 diem C nam giua A va B sao cho AC < CB. Cac diem D va E theo thu tu la trung diem cua Ac Va Cb.Goi I la trung diem cua doan DE. Hay chung to rang I la diem nam giua hai diem E va C
cho doan thang AB va trung diem M cua no a. chung minh rang neu C la diem thuoc tia doi cua tia BA thi CM= (CA +CB)/2 b. chung to rang neu C la diem nam giua M va B thi CM =( CA -CB )/2
cho doan AB=5cm,m la diem thuoc tia doi tia BA.goi I va K lan luot la trung diem cua MA va MB.
a) chung to MB<MA
b)chung to K nam giua M va I
c)tinh IK
Cho doan thang AB,diem C nam giua 2 diem A va B(AC>CB)Goi M la trung diem cua doan thang AB.Chung to rang MC=(AC-BC)/2
cho doan thang AB=6cm. lay diem M nam giua A va B sao cho AM = 1/3 . tren tia MB lay diem I sao cho MI=1/2 AM .Hãy chung to rằng diem I ko la trung diem cua MB nhung I la trung diem cua AB
HElp me
tren tia xy ve doan thang AB sao cho AB = 6cm. Lay dien M nam giua A và B
a. Tinh do dai doan thang MB biet MA=3 cm. M co la trung diem cua A va B khong vi sao
b. Goi I la trung diem cua MA, J la trung diem cua MB. cho biet M có la trung diem cua IJ khong vi sao
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 doan thang AB, Diem O thuoc tia doi cua tia AB. Goi M, N thu tu la trung diem cua OA, OB.
a) Chung to rang OA < OB
b) Trong ba diem O, M, N diem nao nam giua hai diem con lai?
c) Chung to rang do dai doan thang MN khong phu thuoc vao vi tri cua diem O(O thuoc tia doi cua tia AB)
- Tự vẽ hình nha bn :))
a. Vì ) nằm trên tia đối tia AB => A nằm giữa O và B
=> \(OA+AB=OB\)
=> \(OA< OB\)
b. Trong 3 điểm O, M, N thì M nằm giữa hai điểm còn lại vì:
\(OA< OB\Rightarrow\frac{OA}{2}< \frac{OB}{2}\)
=> \(OM< ON\)
=> O nằm giữa hai điểm còn lại
c. \(MN=ON-OM\)
\(=\frac{AB}{2}-\frac{OA}{2}\)
\(=\frac{AB}{2}\)
=> MN không phụ thuộc vào vị trí của điểm O
cho doan thang AB=8cm lay diem M nam giua hai diem A va B sao cho MB= 5cm .goi E la trung diem cua doan thang MB.Goi F nam giua hai diem O va M sao cho EF=4cm .Tinh MF