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[几何] 三角形1月26日一题

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realnumber posted 2015-1-26 10:45 |Read mode
QQ图片20150126104352.png QQ图片20150126104352.png

关于本题,还有个疑问,此处答案含m还是不含m(也就是说把m看作常量,还是变量)?
题目来自浙江严州中学2015年1月阶段测试.

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original poster realnumber posted 2015-1-26 10:56
Last edited by realnumber 2015-1-26 11:02(同事韩的做法)两边分别和$\vv{AB},\vv{AC}$作数量积,
得到方程组$m^2=2m^2x-y,\frac{1}{m^2}=-x+\frac{2y}{m^2}$
解得$3x=\frac{1}{m^2}+2,3y=2+m^2$,看来m是变量,后面略.

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original poster realnumber posted 2015-1-26 11:55
M为AB中点
$\vv{AB}·\vv{AO}=\vv{AB}·{(\vv{AM}+\vv{MO})}=0.5{\vv{AB}}^2$

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