VABCD是一個高20cm的直立棱錐,它的底ABCD是一個長方形,其中AD=21CM,AB=20CM，O是兩條對角線AC與BD的交點；
求平面VAB與平面VAD的交角
－－－－－－－空間－－－－－－－－
2007-01-31 1:07 am
回答 (2)
2007-01-31 6:38 am
✔ 最佳答案
edge line length for long side=((21/2)^2+20^2)^0.5
=22.59cm
edge ling length for short side
=((20/2)^2+20^2)^0.5
=22.36cm
diagonal base plate length
= (21^2+20^2)^0.5
=29cm
The angle betwen two plates (using cos law to calculate)
= arcos(169.28/1010.23)
=80.35 degree.
圖片參考：http://hk.yimg.com/i/icon/16/3.gif
收錄日期: 2021-04-12 20:15:02
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070130000051KK01964