1 . 如图,四边形
是平行四边形,
是对角线
(1)基本尺规作图:过点
作
于点
,再在线段
上截取
.(尺规作图,保留作图痕迹,不写作法)
(2)连接
、
、
,猜想四边形
的形状,将下面的推理过程补充完整.
证明:∵四边形
是平行四边形,
∴
,①__________,
∴
.
在
和
中,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72179b99f0b14e4e04214adbb0c02bc7.png)
∴
,
∴
,②___________.
∴
.
∴③__________
∴四边形
是④__________.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/9/16/f66a9bfd-cb31-451c-9aff-c00ef3f283f4.png?resizew=169)
(1)基本尺规作图:过点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d320f180419175d75eebc618cc458b39.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/607cfabc1d421835b6b64109ad18f571.png)
(2)连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d004d2d115b477ade6af7ddb93db0df8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/274cf35acb4a1748d15c39d15a9bea7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2330c01a4d2b5b20f106e3e48834d5c0.png)
证明:∵四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cfb27272b4eb9ed057dd3b4d40697e7c.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5e1dc3473ec67beb52aaaba5645cacb.png)
在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e742966e3711cfa53dce04022acf4bcc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5df7626240940eb340420a605e95aeee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72179b99f0b14e4e04214adbb0c02bc7.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d99bb3ab66b8884bf23cffe1bddcb33.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/92034dd2bb9480b18709d01153467f8f.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc61ded2b8ea5dea2fd9bc17c409a59c.png)
∴③__________
∴四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/466a12cf2d11494ec4f7173e904932a9.png)
您最近一年使用:0次
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2 . 给出以下四个命题:
①斜棱柱的侧面展开图一定是一个平行四边形;
②若直线
与直线
异面,且
平面
,则
与
的位置关系是平行或相交;
③如果两条平行线中有一条平行于这个平面,那么另外一条直线也平行于该平面;
④若正方体的截面形状是四边形,则该四边形必有一组边平行.
其中正确的命题是______ .(填写序号).
①斜棱柱的侧面展开图一定是一个平行四边形;
②若直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8edaf5492ffc6db02fd5968b643c8b63.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
③如果两条平行线中有一条平行于这个平面,那么另外一条直线也平行于该平面;
④若正方体的截面形状是四边形,则该四边形必有一组边平行.
其中正确的命题是
您最近一年使用:0次