I
iquynh


xin mo hang 2 bài
!!
1.cho tu giac ABCD duong tron tam O tiep xuc voi canh AB,CD thu tu tai A,C va cat BC,AD thu tu tai E,F, chung minh AC,BD,EF dong quy
2. cho tam giac ABC truc am H ke cac duong thang AA',BB',CC' sao cho cac tia phan giac cua goc A'AH,B'BH,C'CH song song voi nhau chung minh AA',BB',CC' dong quy tai mot diem thuoc duong tron ngoai tiep tam giac ABC
1.cho tu giac ABCD duong tron tam O tiep xuc voi canh AB,CD thu tu tai A,C va cat BC,AD thu tu tai E,F, chung minh AC,BD,EF dong quy
2. cho tam giac ABC truc am H ke cac duong thang AA',BB',CC' sao cho cac tia phan giac cua goc A'AH,B'BH,C'CH song song voi nhau chung minh AA',BB',CC' dong quy tai mot diem thuoc duong tron ngoai tiep tam giac ABC
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