1題 f.4 maths question 10M
2011-03-09 2:16 am
圖片參考：http://img36.imageshack.us/img36/7471/64791566.jpg
please teach me how to prove it
i have tried many times but still cannot
thank you
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回答 (1)
2011-03-10 1:27 am
✔ 最佳答案
a) By the given △BDE ≡ △FDC , we have :BD = FD ......(1)CD = ED ......(2)ㄥBDE = ㄥFDCㄥBDE - ㄥFDE = ㄥFDC - ㄥFDE
ㄥBDF = ㄥCDE .......(3)By (1) , (2) , (3) :
△BDF and △CDE both are isos. Δ with the same upper angle.So△BDF ~ △CDE (S.A.S.)Therefore ㄥFBD = ㄥCED since the base ㄥ of a pair similar isos. Δ are equal.And hence :ABDE is a cyclicquad (ext.∠= int. opp.∠)
b)Similarly ,ㄥDCE = ㄥDFB ,CDFA is a cyclicquad (ext.∠= int. opp.∠)
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