Cho tứ giác ABCD

bai 6 cho hinh ve benbiet bm = 9 , ma=6 , bn =12 , nc = 8
A) chung minh  mn//ac
B)chung minh va viet cac day ti so dong dang
   

bai 7
Cho tu giac abcd co ab = 8cm , bc= 3cm , cd = 2 cm , ad=6 cm , va bd = 4 cm
Chung minh tam giac abd dong dang tam giac bdc


Bai 8  
Tam giac abc co 3 duong trung tuyen cat nhau tai o goi p , q , r thu tu  la trung diem cua cac doan thang oa ,ob ,oc 
Chung minh tam giac pqr dong dang tam giac abc


Bai 11 chung minh rang neu tam giac a'b'c' dong dang voi tam giac abc theo ti so k thi ti so hai duong trung tuyen tuong ung bang k