1.Use a vector proof to show that the sum of the squares of diagonal lengths of a quadrilateral is equal to twice the sum of the squares of the lengths of the line segments joining the midpoints of opposite sides.
2. In the diagram (http://hk.geocities.com/sinyeeangela/DSCN5797_1.jpg) ABCD, is a square. M is the midpoint of DC, and AN 垂直 MB. Prove that DN=DA
thank you very much！幫幫忙！
maths 趕！幫忙！10點！
2007-04-18 12:42 pm
回答 (1)
2007-04-18 6:34 pm
✔ 最佳答案
1.(1) 圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/April07/Crazyvector1.jpg
which is the required result.
(Note: Those quantities marked in bold are vector quantities.)
(2)
圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/April07/Crazyvector2.jpg
參考: My Maths knowledge
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