我而家f4 呢題唔識計 教到可用cyclic quad.
http://hk.geocities.com/loklok0206/6d_16.JPG
求助！一題數學圓形數
2007-05-19 6:38 am
回答 (2)
2007-05-19 7:07 am
✔ 最佳答案
39度.Let CBE be x
CBE=CEB
CEB=x
EBD=90(semi-circle)
180-EBD-CBE=ABD
180-90-x=ABD
90-x=ABD
BCE=180-CBE-CEB=180-2X
BCE=ADB
ADB=180-2X
ADB+ABD+27=180
180-2x+180-90-x+27=180
-3x=-117
x=39
2007-05-19 7:19 am
Since DE is a diameter,
∠EBD=90˚
∴∠DBA=90˚-27˚
=63˚
∠CBE+90˚+∠DBA=180˚( adj. ∠s on st.line)
∠CBE=180˚-90˚-63˚
= 27˚
∠EBD=90˚
∴∠DBA=90˚-27˚
=63˚
∠CBE+90˚+∠DBA=180˚( adj. ∠s on st.line)
∠CBE=180˚-90˚-63˚
= 27˚
參考: MYSELF
收錄日期: 2021-04-29 18:14:39
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070518000051KK04620