數學vector
2011-09-26 6:38 am
Suppose the position vectors of points X and Y are x and y respectively. Z is a point on XY with a position vector z=mx+ny. Given that m+n=1.Let x=i+4j,y=2i-j and the angle between OY and OZ is 30度. I have already proved that 239m^2+20mn-25n^2=0 and 194m^2+70m-25=0 . A and B are two points on the line XY such that OA and OB make 30度 with OY. Find OA.OB
回答 (1)
2011-09-27 5:22 am
✔ 最佳答案
http://i1090.photobucket.com/albums/i376/Nelson_Yu/int2-16.jpg圖片參考：http://i1090.photobucket.com/albums/i376/Nelson_Yu/int2-16.jpg
2011-10-01 09:14:18 補充：
I read the question incorrectly. OA.OB can be obtained by getting the dot product of the above 2 vectors to give 405/97.
A better method:
http://i1090.photobucket.com/albums/i376/Nelson_Yu/int2-32.jpg
收錄日期: 2021-04-23 23:26:22
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110925000051KK01131