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meolunngocnghechkute98
2 năm trước
mn giải giúp ạ Bài tập 4: Cho đường tròn ( O; 3cm) và A là một điểm cố định thuộc đường tròn. Đường thẳng d tiếp xúc với đường tròn tại A. Trên d lấy điểm M ( với M khác A). Kẻ dây cung AB vuông góc với OM tại H. a) Tính độ dài OM và AB khi OH = 2cm. b) Chứng minh tam giác MBA cân và MB là tiếp tuyến của ( O ). c) Kẻ đường kính AD, đoạn thẳng DM cắt đường tròn tại E. Chứng minh 2MAMH.MOME.MD . Từ đó suy ra EHMODM . d) Tìm vị trí của điểm M trên d sao cho diện tích tam giác HOA lớn nhất. có hình vẽ nha
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