数学题:已知D是△ABC的边BC上的点,满足向量CD=2向量DB

已知D是△ABC的边BC上的点,满足向量CD=2向量DB,p是线段AD上的动点,若向量AP=x向量AB+y向量AC(xy不等于0),则y/x=?
要具体过程

解:向量CB=向量AB-向量AC,
向量CD=2/3向量CB=2/3向量AB-2/3向量AC,
向量AD=向量AC+向量CD=2/3向量AB+1/3向量AC,
向量AP=t向量AD=2t/3向量AB+t/3向量AC,
x=2t/3,y=t/3,所以y/x=1/2.
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第1个回答  2011-05-12
直接去计算就可以了,不过要建好坐标
第2个回答  2011-05-12
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第3个回答  2011-05-12
d是BC的三等分点,没笔和纸下面的我就无能为力了,你建坐标系也可以做,提示,可以假设是特殊三角形
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