Cho
ABC, ke AD vuong goc voi AB va AD bang AB (C va D khc phia AB) ke Ay vuiong goc voi AC ( Ay va AB thuoc 2 nua mat phang doi nhau bo AC) ke duong thang di wa A va trung diem M cua BC. Tu D ke uong vuong goc voi AM tai E cat Ay tai F. Ke By vuong goc voi AM, CK vuong goc voi AM.
CMR:
ACF la` tam giac vuong can
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