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npson1
2 năm trước
Cho tam giác ABC . Kẻ BE ⊥ AC và CF ⊥ AB . Biết BE=CF=8cm ; độ dài các đoạn thẳng BF và BC tỉ lệ với 3 và 5 . a) b) c) Chứng minh tam giác ABC là tam giác cân Tính độ dài cạnh đáy BC BE và CF cắt nhau tại O . Nối AO và EF . Chứng minh đường thẳng AO là đường trung trực của đoạn thẳng EF.
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