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TRƯỚNG THỰC HÀNH SÀI GÒN ĐỀ KIỂM TRA 1 TIẾT HKII (2009-2010)
MÔN: TOÁN (HÌNH HỌC)
THỜI GIAN : 45 PHÚT

Điểm
 Lời phê của thầy ( cô ) giáo
Chữ kí PHHS





 ĐỀ BÀI
Cho đường tròn tâm (O;R) và một điểm A ở ngoài đường tròn sao cho OA= 3R. Từ A vẽ hai tiếp tuyến AB,AC đến đường tròn (O) với B,C là hai tiếp điểm.
Chứng minh tứ giác OBAC là một tứ giác nội tiếp.
Từ B vẽ các đường thẳng song song với AC , Cắt đường tròn (O) tại điểm D(khác điểm B). Đường thẳng AD cắt đường tròn tại E ( khác điểm D) . Chứng minh AB2=AE.AD
Chứng minh tia đối của tia EC là tia phân giác của góc BEC.
Tính diện tích của tam giác BDC theo R.
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