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namhongson505
2 năm trước
Cho hai đường tròn (O) và (O’) tiếp xúc ngoài tại A. Kẻ tiếp tuyến chung DE, D thuộc đường tròn tâm O, E thuộc đường tròn tâm O’. Kẻ tiếp tuyến chung trong tại A, cắt DE ở I. Gọi M là giao điểm của OI và AD, N là giao điểm của O’I và AE. a, Tứ giác AMIN là hình gì? Vì sao? b, Chứng minh IM.IO=IN.IO’ c, Chứng minh rằng O O’ là tiếp tuyến của đường tròn có đường kính là DE. d, Tính độ dài DE biết rằng OA=5cm, O’A=3,2 cm. HELP me . Mình cần gấp trong hôm nay !!!
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