有一條求證題

2011-01-10 5:32 am

圖片參考:http://imgcld.yimg.com/8/n/HA06289096/o/701101090123513873438230.jpg
AEB 和BDC 係直綫,AC=BC,AD 係角BAC 既角平分綫,DE 垂直AB 及AC 垂直BC A. 求證 DC =DE B 若AB 係8CM ,求三角形BDE 周界
更新1:

樓下唔係aas 咩?

回答 (5)

2011-01-10 6:03 am
✔ 最佳答案
A)AD = AD (公共)
ㄥDAE = ㄥDAC (已知)
ㄥDEA = ㄥDCA = 90° (已知)△DAE ~= △DCA (A.S.A)對應邊 DC =DE 。
B)△BDE 周界= EB + BD + DE
= EB + BD + DC
= EB + BC
= (AB + BC + CA) - (EA + AC) , △DAE ~= △DCA 故 EA = AC ,
= (8 + 2BC) - (2AC)
= (8 + 2BC) - (2BC)
= 8

2011-01-09 22:06:47 補充:
三角形BDE 周界
= 8CM

2011-01-09 22:12:17 補充:
B)

另法 :
△BDE 周界
= EB + BD + DE
= EB + BD + DC
= EB + BC
= EB + AC , △DAE ~= △DCA 故 EA = AC ,
= EB + EA
= AB
= 8 CM

2011-01-09 22:51:57 補充:
aas , sas 好像不一定要順序?
sorry不太肯定。
2011-01-11 12:49 am
證明全等的時候需依據已證條件的排列次序,順逆時針皆可。
2011-01-10 7:19 am
It should be AAS
2011-01-10 7:02 am
不打緊,我明天再問老師吧,但係始終都係thx u 幫我解決左個難題
2011-01-10 6:02 am
只有AB=8 cm?


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