Please find out my mistake

👨🏻‍🏫 學術台數學

Henry

2011-03-28 3:57 am

http://img827.imageshack.us/i/maths6.jpg/
Find the angle between the planes FCD and FCH

My method:
http://img840.imageshack.us/i/maths7.jpg/
the angle between the planes FCD and FCH
is angle DIH

First,find the length of DI
Then,find the length of IH
Third,find the length of DH
Finally,use cosine formula

But I cannot find the answer(120degree cor. to 3 sig fig.)
Can anyone point out the mistake I made?
Thx~

回答 (1)

用戶9112

2011-03-28 4:16 am

✔ 最佳答案

http://i1090.photobucket.com/albums/i376/Nelson_Yu/1-172.jpg

圖片參考：http://i1090.photobucket.com/albums/i376/Nelson_Yu/1-172.jpg

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