chung minh rang trong hinh thang doan thang trung diem cua hai duong cheo luon song song voi hai day va nua hieu hai day
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BAI1Cho tam giac deu ABC .Diem M nam trong tam giac do.Qua M ke duong thang song song voi AC va cat BC o D,ke duong thang song song voi AB va cat AC o D,ke duong thang song song voi BC va cat AB o F.CMRa,BFMD,CDME,AEMF LA CAC HINH THANG CANb,goc DMEgoc EMFgoc DMFc,Trong ba doan thang MA,MB,MC doan lon nhat nho hon tong hai doan kiaBAI2Hinh thang can ABCD (AB//CD)co hai duong cheo cat nhau tai P,hai canh ben keo dai cat nhau tai Q .CMRPQ la duong trung truc cua hai day
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BAI1
Cho tam giac deu ABC .Diem M nam trong tam giac do.Qua M ke duong thang song song voi AC va cat BC o D,ke duong thang song song voi AB va cat AC o D,ke duong thang song song voi BC va cat AB o F.CMR
a,BFMD,CDME,AEMF LA CAC HINH THANG CAN
b,goc DME=goc EMF=goc DMF
c,Trong ba doan thang MA,MB,MC doan lon nhat nho hon tong hai doan kia
BAI2
Hinh thang can ABCD (AB//CD)co hai duong cheo cat nhau tai P,hai canh ben keo dai cat nhau tai Q .CMR
PQ la duong trung truc cua hai day
Cho hinh ABCD Trong khoang giua hai day AB va CD cua hinh thang do nguoi ta them ke 8 duong thang song song voi 2 day cac duong thang do khong trung nhau va khong trung voi day AB va CD cac duong thang va cat canh 2 ben cua hinh thang ABCD tao ra nhung hinh thang moi
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Cho hinh thang ABCḌ̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣̣(AB//CD),O la giao diem cua hai duong cheo AC va BD. Qua O ke duong thang song song voi AB cat AD va BC lan luot o M va N. CHung minh OM = ON
ảnh đây nhé, nếu ko thấy thì vào thống kê hỏi đáp của mik xem ảnh nhé
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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chung minh rang trong hinh thang vuong, hieu cac binh phuong hai duong cheo bang cac binh phuong hai day
Xét hình thang cân ABCD có đáy nhỏ AB = m, đáy lớn CD = n, đường cao AH = BK = h, DH = KC = a ---> CD = n = m + 2a
Theo định lý Pythagore, ta có :
AC^2 = AH^2 + HC^2 (1)
AD^2 = AH^2 + DH^2 (2)
---> AC^2 - AD^2 = HC^2 - DH^2 = (m+a)^2 - a^2 = m^2 + 2m.a = m(m+2a) = m.n = AB.CD (đpcm)
đơn giản như đan rổ
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Cho tam giac ABC. Duong thang qua B song song voi AC cat duong thang qua C song song voi AB tai D
a) Chung minh rang tu giac ABDC la hinh binh hanh
b) Goi M la trung diem canh BC. Chung minh rang 3 diem A,M,D thang hang
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cho hinh thang ABCD. tren AB lay 2 diem M va N ke hai duong sao cho doan AM=ND=AD/4. Tu M va N ke 2 duong song song voi AB va CD, chung cat canh BC tai P va Q. Noi NP,QN. hay chung to rang dien tch hinh thang MPQN=1/2 dien tich hinh thang ABCD
cho hinh thoi ABCD ,goi O la giao diem cua hai dong cheo ACva BD .qua B ve duong thang song song voi AC,qua C ve duong thang song song voi BD ,chung cat nhau tai I
a)chung minh OBICla hinh chu nhat?
b)chung minh AB=OI
c)tim dieu kien cua hinh thoiABCDde tu giac OBIC la hinh vuong
cho hinh thang ABCD ,goi I la trung diem cua duong cheo AC,K la trung diem cua duong cheo BD.chung minh IK song song voi ab song song voi CD