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1992年7月号问题解答 (解答由供题人给出) 27.AB、AC切⊙O于B、C两点,过OA与BC的交点M任作⊙O的弦EF。试证:①△AEF与△ABC有公共内心; ②△AEF与△ABC有一个旁心也重合。
The July 1992 issue (Answer is given by the donor) 27. AB, AC cuts O to B, C, and passes OA and BC intersection point M as ⊙O’s chord EF. Testimony: 1 △ AEF and △ ABC have a common heart; 2 △ AEF and △ ABC have a side of heart also coincide.