作者Honor1984 (奈何上天造化弄人？)
看板Math
标题Re: [中学] 请教一下这题怎麽解
时间Mon Oct 13 01:01:41 2025
※ 引述《math365 (math365)》之铭言：
: https://ibb.co/1YRBZmRJ
: 国中相似形的单元，麻烦大家帮忙一下，谢谢
过D分别做BA和BE的平行线交AC於J、H => EH = 5
J、H对BC的垂足分别为D'、F'
令AG = GD = a，JH = 5r，HC = t => r = t/(5 + t)
△HF'C ~ △ADC => 6r/t = 2a/(10 + t) => a = 3(10 + t)/(t + 5)
DA^2 = AJ * AC => (2a)^2 = (10 - 5r)(10 + t) => t = 11/5
=> EC = 5 + t = 36/5
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