Mot hinh thang co hai day khong bang nhau chung minh rang
a)tong hai goc ke day nho be hon tong hai goc ke day lon
b)tong hai canh ben > hieu hai cach day
Mot hinh thang co hai day khong bang nhau chung minh rang
a)tong hai goc ke day nho be hon tong hai goc ke day lon
b)tong hai canh ben > hieu hai cach day
Câu b:
Trong hình thang ABCD (AB//CD)
Kẻ BE//AD
Ta có:
BE=AD (hình thang có 2 cạnh bên song song)
Trong ΔBEC có:
BC+BC>EC
Hay AD +BC >CD-AB
Cho hinh thang ABCD, day nho CD bang tong hai canh ben AD&BC. C/m: Cac duong phan giac cua goc A va goc B cat nhau tai mot dien tren CD
cho hinh thang ABCD(AB//CD)
a)chung minh rang neu hai tia phan giac cua hai goc A va D cung di qua trung diem F cua canh ben BC thi canh ben AD bang tong hai canh day
b) chung minh rang neu AD=AB+CD thi tia phan giac cua hai goc A va B cat nhau tai trung diem cua canh ben BC
cho hinh thang ABCD co canh ben AD vuong goc voi hai day Day nho AB dai 12cm day lon DC bang 36cm Chieu cao bang trung binh cong hai day nguoi ta keo dai day nho AB them mot doan BE sao cho AE = DC tinh dien tich tam giac BEC.
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
Hinh thang co tong do dai hai day bang 30,5dm, day lon bang 1,5 lan day be, chieu cao hon day be 6,2dm. Tinh dien tich hinh thang
hinh thang abcd co day be la 1,8dm day lon hon day be 0,6dm chieu co bang 1/3 tong hai day tinh dien tich hinh thang abcd
mot thua ruong hinh thang co day lon dai 240m day be ngan hon day lon 80m chieu cao bang 1/4 tong do dai hai day .biet rang nang xuat lua thu hoach duoc la 8,4tan tren mot hec ta . tinh so lua thu hoach tren thua ruong do
a)Mot hinh tam giac ABC co day BC la 34,5dm. Neu keo dai canh BC ve phia C mot doan bai 7 dm thi dien tich tang them 42 dm2 .Tinh dien tich hinh tam giac ABC.
b)Mot hinh thang co tong hai day la 78dm,day lon bang 7/6 day nho .Chieu cao bang 1/2 day lon .Tinh dien ich hinh thang do