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![](https://rs.olm.vn/images/avt/0.png?1311)
17 tháng 3 2018
Cho tam giác ABC có diện tích 120 cm2 . D là điểm chính giữa cạnh AB trên cạnh AC lấy điểm I sao cho AI = 1/3 AC . Tính diện tích tam giác DAI
đáp án : 20 cm2
![](https://rs.olm.vn/images/avt/0.png?1311)
27 tháng 7 2015
Nối C với M
Tam giác ACM và tam giác ACB có chung đường cao hạ từ C xuống cạnh AB; đáy AM = 1/2 đáy AB (Vì M là điểm chính giữac cạnh AB)
=> S (ACM) = 1/2 S(ABC) = 1/2 x 160 = 80 cm2
Xét tam giác AMN và tam giác ACM có chung chiều cao hạ từ M xuống cạnh AC; đáy AN = 1/4 đáy AC
=> S (AMN) = 1/4 x S (ACM) = 1/4 x 80 = 20 cm2
Tam giác ABC có diện tích là 120 cm2 .D là điểm chính giữa của cạnh AB.Trên cạnh AC lấy điểm I sao cho AI=1/3 AC.Tính diện tích tam giác DAI.![](data:image/png;base64,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)
ĐÁP ÁN : 20cm2
20 cm2