Help me for this math

2014-01-08 3:56 am
In the figure,ABC and EDC are stragiht lines,AB=AD=AE,angle BAD=42degree and angle DAE=54degree
(a)Find angle BEC
(b)Is BCE an isosceles triangle?

Thx for help!!

回答 (2)

2014-01-08 5:27 am
✔ 最佳答案

(a) ∠BAE = ∠BAD + ∠DAE = 42 + 54 = 96
In ΔBAE, as AB = AE, so
∠AEB = (180 - 96)/2 = 42 ...... (1)In ΔDAE, as AD = AE, so∠AED = (180 - 54)/2 = 63 ...... (2)So, ∠BEC = ∠AEC - ∠AEB= 63 - 42 ...................... (from (1), (2))= 21
(b) In ΔAEC∠ACE= 180 - ∠EAC - ∠AEC= 180 - 96 - 63= 21 ...................,,,,,,,,,.......... (3)In ΔBCE, as ∠BCE = 21 (from (3)) and ∠BEC = 21 (from (a)), so, BE = BC, therefore ΔBCE is an isosceles triangle

2014-01-08 21:49:54 補充:
跟題目講,照著畫就是了。
先畫AB=AD=AE, BAD=42, DAE=54, 延長BA及ED, 交於C, 完成。
2014-01-08 4:34 am
圖在哪?~~~~~~~~~~~~~

2014-01-08 17:42:45 補充:
那些年 :

大大,圖都沒有,你怎麽做的呀!


收錄日期: 2021-04-27 20:40:47
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20140107000051KK00181

檢視 Wayback Machine 備份