名校
1 . 在
中,角
所对边分别为
,若
.
(1)证明:
为等边三角形;
(2)若(1)中的等边
边长为2,试用斜二测法画出其直观图,并求直观图面积.
注:只需画出直观图并求面积,不用写出详细的作图步骤.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ec3f79448524d6848be51fdd5c7a150.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb1b5305cb9b5a90c4f13bceaaee4fc0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8176a512a8e931c56d85607764f48851.png)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
(2)若(1)中的等边
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
注:只需画出直观图并求面积,不用写出详细的作图步骤.
您最近一年使用:0次
2014·吉林·一模
2 . 一个多面体的直观图及三视图如图所示,其中
分别是
的中点,
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/30/478004d6-0050-48ca-9182-b1b1824dddcf.png?resizew=172)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/30/cbb855ed-264b-41ad-82c0-f848f0f70138.png?resizew=174)
(1)求证:
平面
;
(2)求二面角
的余弦值;
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7789a500686c7a73770404ead6af0590.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31e4c8af36ed081c96928dc7d8d9012e.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/30/478004d6-0050-48ca-9182-b1b1824dddcf.png?resizew=172)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/30/cbb855ed-264b-41ad-82c0-f848f0f70138.png?resizew=174)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/edcf19a7f0dd0cdf59516ae585025110.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b32c05247f6998d7a70d31d13be4148c.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f3fb82553d568ea8aae9d0dd89ae1ca2.png)
您最近一年使用:0次