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dinhnhanha02032000
2 năm trước
Cho tam giác ABC cân tại A nội tiếp đường tròn tâm O . Đường cao AH cắt đường tròn ở điểm D. a) AD có phải là đường kính của đường tròn tâm O không ? Tại sao? b) Chứng minh BC ^2 = 4AH . DH c) Cho BC= 24cm, AB=20cm. Tính bán kính của đường tròn tâm O.
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