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letin1207
2 năm trước
Cho ΔABC cân tại A (AB > BC) có M, N là trung điểm của AB, AC. a) Chứng minh rằng : MN // BC và MBCN là hình thang cân. b) BN cắt CM tại O. Trên tia BN lấy điểm E sao cho O là trung điểm của BE. Trên tia CM lấy điểm D sao cho O là trung điểm của CD. Chứng minh rằng : OB = OC và DBCE là hình chữ nhật.
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