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6个未知量的求解,求大佬帮忙看看

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k10 posted 2021-6-7 20:49 |Read mode
空间中一刚体矩形平台
21e.png
ABCD4点坐标分别为
A(-550,-960,4020)
B(-500+a,1000+b,4040)
C(500+c,-1000+d,4040)
D(500+e,1000+f,4020)
求abcdef,6个未知量
麻烦给出具体的计算步骤
万分感谢!!!

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original poster k10 posted 2021-6-7 21:18
补充条件:AB=2000,AC=1000

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爪机专用 posted 2021-6-8 08:34
有问题,按你图上标的字母顺序,有 `\vv{AB}=\vv{CD}`,但就 z 坐标明显不成立。

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original poster k10 posted 2021-6-8 10:50
是的,不好意思
是这种情况
ABCD4点坐标分别为
A(-500+20,-1000,4040)
B(-500+a,1000+b,4040)
C(500+c,-1000+d,4000)
D(500+e,1000+f,4000)

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kuing posted 2021-6-8 15:02
回复 4# k10

那还是不足以确定 abcdef

构成矩形等价于 `\vv{AB}=\vv{CD}` 且 `\vv{AB}\cdot\vv{AC}=0`,再加上长宽的条件,构成方程组
\[\led
&20-a=c-e,\\
&{-2000-b=-2000+d-f},\\
&(20-a)(-980-c)+(-2000-b)(-d)=0,\\
&(20-a)^2+(-2000-b)^2=2000^2,\\
&(-980-c)^2+(-d)^2+40^2=1000^2,
\endled\]不够方程数。

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