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ngocanhtbdhsp
2 năm trước
Cho đường tròn tâm O bán kính R, điểm A ở ngoài đường tròn. Qua A kẻ tiếp tuyến AB với (O; R) (B là tiếp điểm). Kẻ đường kính BC, nối AC cắt (O) tại điểm thứ hai là E. 1) Chứng minh rằng: EC.AC = 4R^2 2) Qua A kẻ tiếp tuyến AM với (O) (M là tiếp điểm). Chứng minh rằng: MC // AO. 3) Qua O kẻ đường vuông góc với MC cắt AM kéo dài tại K. Chứng minh rằng: KC là tiếp tuyến (O) 4) Chứng minh rằng: BC là tiếp tuyến đường tròn đường kính AK. Giúp mình với nha Cảm ơn ạ <3
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