1 . 比利时数学家旦德林发现:两个不相切的球与一个圆锥面都相切,若一个平面在圆锥内部与两个球都相切,则平面与圆锥面的交线是以切点为焦点的椭圆.如图所示,这个结论在圆柱中也适用.用平行光源照射一个放在桌面上的球,球在桌面上留下的投影区域内(含边界)有一点
,若平行光与桌面夹角为
,球的半径为
,则点
到球与桌面切点距离的最大值为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ac09dc1ca2cdd7aef28c218763d3e4d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4aa0df7f1e45f9de29e802c7f19a4f64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/6/3/b374eb55-8e11-493f-9292-560f46555500.png?resizew=76)
A.![]() | B.![]() | C.![]() | D.![]() |
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2 . 如图,等腰直角三角形
在平面
上方,
,若
以
为旋转轴旋转,形成的旋转体在平面
内的投影不可能的是( )
![](https://img.xkw.com/dksih/QBM/2021/5/6/2715425529528320/2731352577867776/STEM/a030439c-7e8e-4ec6-9282-890f5d73d401.png?resizew=224)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f8e9ec412ea0355e4e5cd06c60e5fee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://img.xkw.com/dksih/QBM/2021/5/6/2715425529528320/2731352577867776/STEM/a030439c-7e8e-4ec6-9282-890f5d73d401.png?resizew=224)
A.![]() | B.![]() | C.![]() | D.![]() |
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