maths~~~~~

👨🏻‍🏫 學術台數學

用戶7639

2010-03-27 2:08 am

As follows:

圖片參考：http://j.imagehost.org/0704/ScreenHunter_05_Mar_25_12_43.gif

回答 (1)

STEVIE-G™

2010-03-27 9:01 pm

✔ 最佳答案

Since EF=FG, then EG=2FG
AGtan BAD=2(AGtan CAD)
tan BAD=2tan CAD...(*)

For condition I,
In tri ABD, BD/AD=tan BAD -> BD=ADtan BAD
In tri ACD, CD/AD=tan CAD -> CD=ADtan CAD
So, BD/CD=2...Hence (I) is correct

For condition II,
It is wrong as 中線必須由頂點連接

For condition III,
因為AD是三角形ABC的高,所以正確

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