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chiencuonglk
2 năm trước
Cho hình thang vuông ABCD có AB//CD (góc A=90 độ),AB=4cm,CD=9cm,AD=6cm 1.CM: tam giác BAD đồng dạng tam giác ADC 2.CM:AC vuông góc BD 2.Cho tam giác ABC vuông tại A có AH là đường cao(H thuộc BC)kẻ HD vuông AC tại D(DE thuộc AC) 1. CM: tam giác DHA đồng dạng HAC 2. Gọi O là trung điểm AB, OC cắt AH,HD lần lượt tại K và I. Chứng minh: HI=ID 3. Chứng minh: AD.AC=BH.HC
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