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loga2017
2 năm trước
Cho tam giác ABC có ba góc nhọn. Vẽ các đường cao BD và CE chúng cat nhau tại H. a. Chứng minh tứ giác AEHD nội tiếp đường tròn. b. Chứng minh: AE.AB = AD.AC . c. Gọi K là trung điểm của DE, I là trung điểm của BC, J trung điểm AH. Chứng minh ba điểm K,I,J thẳng hàng. Mọi người giải giúp mình với ạ !
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