问题: 48th IMO (2007)
2.
Consider five points A,B,C,D and E such that ABCD is a parallelogram and BCED is a cyclic quadrilateral. Let l be a line passing through A . Suppose that l intersects the interior of the segment DC at F and intersects line BC at G. Suppose also that EF=EG=EC . Prove that l is the bisector of angle DAB.
解答:
标准答案是用的反证法,但是如果从E向三角形BCD做一条西姆松(Simson)线的话就很容易得出结论了.
附:今年IMO第6题有点欺负人......
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