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
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cho đoạn thẳng AB va trung diem M cua no
a) CMR:Neu C la diem thuoc tia doi cua tia BA thi CM= \(\frac{CA+CB}{2}\)
b)CMR:neu C la diem nam giua hai diem M va B thi CM= \(\frac{CA-CB}{2}\)
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
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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...
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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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tren doan thang AC co do dai 12 cm ,lay diem B sao cho AB=5 cm .a, tinh do dai cua doan thang BC.b,goi M,N lan luot la trung diem cua doan thang AB ,BC . tinh do dai doan thang MN.c, lay diem D thuoc tia doi cua tia CA sao cho CD =7 cm . chung to rang diem C la trung diem cua doan thang BD
Cho doan thang AB.Diem C thuoc tia doi cua tia BA.M la trung diem cua doan thang AB
a ) Chung to rang : CM =\(\frac{CA+CB}{2}\)
b ) Goi O la mot diem nam ngoai doan thang AB.Biet goc AOC = 120 do; goc BOC = 30 do;goc AOM = 60 do.Hoi OB co phai la tia phan giac goc MOC khong? Vi sao ?
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 diem O thuoc tia doi cua tia AB goi M,N theo 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 ko phu thuoacvao vi tri cua diem O ( O thuoac tia doi cua tia AB)
Tren tia Ox lay hai diem A,B sao cho OA = 2cm, OB = 9cm
a) chung to A nam giua hai diem O va B va tinh do dai AB
b) Tren tia Oy la tia doi cua Ox lay diem C sao cho OC = 5cm. tinh do dai CA
c) chung to A la trung diem cua doan thang CB
Cho doan thang AB.Diem O thuoc tia doi cua AB.Goi M,Ntheo thu tu la trung diem cua OA,OB
a,Chung minh OA<OB
b,Trong 3 diem M,O,N diem nao nam giua 2 diem con lai
c,Chung to rang do dai doan thang MN khong phu thuoc vao vi ri diem O(O thuoc tia doi cua AB)
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