Cho tam giác ABC nhọn , 2 đường cao BD và CE cắt nhau tại H . CM : a, tam giác ABD đồng dạng tam giác ACE => AE.AB = AD.AC b, AH kéo dài cắt BC tại F . Cm AF vuông góc BC và BH.BD = BF.BC ( mọi người giúp e vs ạ , e đang cần gấp )

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