Cho tam giac ABC deu,tren tia doi cua tia CB lay D ve cac tia Cx song song voi AB,Dy song song voi AC,chung cat nhau tai E.Chung minh: a)tam giac CDE deu

b)BE=AD

c) Goi M,N lan luot la trung diem cua BE va AD.Hoi tam giac CMN la tam giac gi?vi sao

Cho tam giac ABC deu,tren tia doi cua tia CB lay D ve cac tia Cx song song voi AB,Dy song song voi AC,chung cat nhau tai E.Chung minh: a)tam giac CDE deu

b)BE=AD

c) Goi M,N lan luot la trung diem cua BE va AD.Hoi tam giac CMN la tam giac gi?vi sao

Cho tam giac ABC deu,tren tia doi cua tia CB lay D ve cac tia Cx song song voi AB,Dy song song voi AC,chung cat nhau tai E.Chung minh: a)tam giac CDE deu

b)BE=AD

c) Goi M,N lan luot la trung diem cua BE va AD.Hoi tam giac CMN la tam giac gi?vi sao

Cho tam giac ABC deu,tren tia doi cua tia CB lay D ve cac tia Cx song song voi AB,Dy song song voi AC,chung cat nhau tai E.Chung minh: a)tam giac CDE deu

b)BE=AD

c) Goi M,N lan luot la trung diem cua BE va AD.Hoi tam giac CMN la tam giac gi?vi sao

Cho tam giac ABC deu,tren tia doi cua tia CB lay D ve cac tia Cx song song voi AB,Dy song song voi AC,chung cat nhau tai E.Chung minh: a)tam giac CDE deu

b)BE=AD

c) Goi M,N lan luot la trung diem cua BE va AD.Hoi tam giac CMN la tam giac gi?vi sao

cho tam giac abc co cac cach khong doi. lay diem d va m tren canh ab sao cho ad = bm. qua d va m ve cac duong thang song song voi bc cat ac lan luot tai e va n. chung minh de+mn khong doi khi d va m di chuyen tren canh ab.

cho tam giac BC AB<Ac tren 2 canh AB,AC lay tuong ung 2 diem D va E sao cho BD=CE goi M,N,I lan luot la cac trung diem cua BC,DE va CD. Duong thang MN cat AB,AC thu tu o P va Q chung minh tam giac MNI va tam giac PQA can

giup minh voi!!!!!!!!!!!!!!!!!!!!!!!!!!

Cho tam giac ABC co AB=AC. Tren cac canh AB va AC lan luot lay cac diem D va E sao cho AD=AE. Cac doan thang BE va CD cat nhau tai K

a, Chung minh rang tam giac ABE= tam giac ACD

b, Chung minh rang tam giac KDB=tam giac KCE

c, Goi I la trung diem canh BC. Chung minh rang cac diemA,K,I thang hang

Cho tam giac deu ABC . Tren tia BC ta lay diem M sao cho CM = BC . Tren tia CA lay diem N sao cho AN=AC va tren tia AB lay diem P sao cho BP = AB

a) AMR : MA vuong goc voi AP

b) CMR : Tam giac MNP la tam giac deu

c) Goi O la tam cua tam giac deu ABC . CMR : ON vuong goc voi MP