As follows:
圖片參考：http://e.imagehost.org/0789/ScreenHunter_02_Mar_03_23_47.gif
http://e.imagehost.org/0789/ScreenHunter_02_Mar_03_23_47.gif
maths~~~~~
2010-03-04 7:53 am
回答 (1)
2010-03-04 8:47 am
✔ 最佳答案
∠DCB + ∠GCB = 180° (同側鄰角) .... (1)∠ABC + ∠GBC = 180° (同側鄰角) .... (2)
BC = GB (同圓半徑)
∠GCB = ∠GBC (等腰ΔGCB 底角)
比較 (1) 和 (2):
∠DCB = ∠ABC (公理)
但 ∠DCB + ∠DAB = 180° (圓內接四邊形內對角)
∠ABC + ∠DAB = 180° (代入)
所以 AD // BC (同側內角互補)
參考: 老爺子
收錄日期: 2021-04-23 20:58:03
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100303000051KK01880