Re: [中學] OMC 複賽 幾何求角度問題
※ 引述《deryann (星辰)》之銘言：
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考慮 ABFD 的內角和 ∠DAB = ∠BFD = 90度 故 ∠ABF + ∠FDA = 180 度
又 E-B-F 共線故 ∠EBA + ∠ABF = 180 度 於是 ∠EBA = ∠FDA
另外 AB = AD 且 ∠EAB = 90度 - ∠BAC = ∠CAD
所以 △EAB 全等於 △CAD (ASA)
由此 AE = AC 故所求角為 45 度
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'You've sort of made up for it tonight,' said Harry. 'Getting the
sword. Finishing the Horcrux. Saving my life.'
'That makes me sound a lot cooler then I was,' Ron mumbled.
'Stuff like that always sounds cooler then it really was,' said
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-- Harry Potter and the Deathly Hollows, P.308
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05/26 13:29, , 1F
05/26 13:29, 1F
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