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问题: 几何

已知:如图,矩形ABCD中,AC与BD交于点O,AF⊥BD,垂足为F,∠BCD的平分线交FA的延长线于点E。求证:AE=AC

解答:

∠ACE =∠BCD/2 -∠ACD =45°-∠ACD
∠AEC =∠CAF-∠ACE =(90°-∠AOF)-∠ACE
= (90°-2*∠ABD)-(45°-∠ACD)
= 45°-2*∠ABD+∠ACD =45°-∠ACD =∠ACE
===> AE=AC