Question

[shiro tsuki]

cho tam giác ABC. trên các cạnh AB,AC lần lượt lấy các điểm E,D sao cho AE/AC=AD/AB=1/3

a, chứng minh tam giác ABD đồng dạng tam giác ACE

b, chứng minh tam giácADE đồng dạng tam giác ABC

c, giả sử I=BD giao EC. chứng minh ID.IB=IE.IC

Answer 1

[Trần Quốc Khanh]

a/ xét 2 tam giác đói có : \(\frac{AE}{AC}=\frac{AD}{AB}\Leftrightarrow\frac{AE}{AD}=\frac{AC}{AB}\), chung góc A

\(\Rightarrow\Delta AEC\sim\Delta ADB\left(c-g-c\right)\)

b/ xét 2 tam giác đó có: \(\frac{AE}{AC}=\frac{AD}{AB}\), chung góc A

\(\Rightarrow\Delta AED\sim\Delta ACB\left(c-g-c\right)\)

Answer 2

[Quang Dung Nek]

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