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20 0 2年 1 0月号问题解答(解答由问题提供人给出 )1 3 96 ⊙Ｏ是△ＡＢＣ的内切圆 .Ｄ、Ｅ、Ｆ是ＢＣ、ＣＡ、ＡＢ上的切点 ,ＤＤ′、ＥＥ′、ＦＦ′都是⊙Ｏ的直径 .求证 :直线ＡＤ′、ＢＥ′、ＣＦ′共点 .(安徽省怀宁江镇中学 黄金福 2 461 42 )证明 设直线ＡＤ′、Ｂ
Answers (problems to be given by the problem provider) for the issue of 1 October issue of 2020 2 1 3 96 ⊙O is the inscribed circle of △ABC. D, E, and F are the cut points on BC, CA, and AB, DD′ , EE′, FF′ are the diameters of ⊙O. Proof: Straight lines AD′, BE′, CF′ are common. (Huining Jiangzhen Middle School Huangjinfu 2 461 42 in Anhui Province) proves to set straight lines AD′, B