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2023-03-12 10:26:19
2023-03-12 10:26:16
2023-03-12 10:26:06
2023-03-12 10:25:58
2023-03-12 10:25:50
2023-03-12 10:23:02
a) ta thấy tỉ số diện tích tam giác ANB/ABC=1/3
tỉ số diện tích tam giác AMN/ANB=1/3 ( có chung chiều cao hạ từ N)
diện tích tam giác AMN là:
b) C với D như hình vẽ
ta thấy diện tích hai tam giác NDE bằng diện tích tam giác NDC ( có chung chiều cao và đáy )
từ đó suy ra:
vậy AND/NDE=1/2