circle

2011-06-11 5:11 pm

圖片參考：http://img805.imageshack.us/img805/8555/14089568.jpg

In the figure, ABCD is a circle. AB produced and DC produced meet at E. If AC and BD intersect at F, then angleABD=?

回答 (2)

用戶25975

2011-06-11 5:25 pm

✔ 最佳答案

Let ∠ABD = x, then ∠ACD = x (∠ in the same segment)

∠ABD + ∠BAF = 82 (Ext. ∠ of triangle)

∠BAF = 82 - x

∠CDF = ∠BAF = 82 - x (∠ in the same segment)

With ∠BAF + ∠CDF + BEC = ∠AFD:

82 - x + 82 - x + 30 = 82

2x = 112

x = 56

參考: 原創答案

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hello

2011-06-12 5:37 am

i give alternative solution, hope it is helpful
http://www.webpagescreenshot.info/img/664187-611201143542pm.png
圖片參考：http://www.webpagescreenshot.info/img/664187-611201143542pm.png

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收錄日期: 2021-04-20 00:45:27
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