在正方形ABCD,A1B1C1D1中,E、F分别为BB1,CC1中点,求异面直线AE,D1F的余弦值
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第1个回答 2012-06-07
求异面直线AE,D1F的余弦值 打漏,是求异面直线AE,D1F夹角的余弦值。
取坐标系 D﹙0,0,0﹚ A﹙1,0,0﹚ C﹙0,1,0﹚,D1﹙0,0,1﹚
则E﹙1,1,1/2﹚ F﹙0,1,1/2﹚
AE=﹛0,1,1/2﹜ D1F=﹛0,1,-1/2﹜
cosα=AE•D1F/﹙|AE|×|D1F|﹚=3/5 ﹙α为异面直线AE,D1F夹角。﹚
取坐标系 D﹙0,0,0﹚ A﹙1,0,0﹚ C﹙0,1,0﹚,D1﹙0,0,1﹚
则E﹙1,1,1/2﹚ F﹙0,1,1/2﹚
AE=﹛0,1,1/2﹜ D1F=﹛0,1,-1/2﹜
cosα=AE•D1F/﹙|AE|×|D1F|﹚=3/5 ﹙α为异面直线AE,D1F夹角。﹚