1 . 将正方形
的边
绕点
逆时针旋转至
,记旋转角为
.连接
,过点
作
垂直于直线
,垂足为点
,连接
,
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/23/86367bb7-74ca-4052-a1c0-d24f5046afed.png?resizew=244)
(1)如图1,当
时,
的形状为 ,连接
,可求出
的值为 ;
(2)当
且
时,
①(1)中的两个结论是否仍然成立?如果成立,请仅就图2的情形进行证明;如果不成立,请说明理由;
②当以点
为顶点的四边形是平行四边形时,请直接写出
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/943712a5e96b16cc15d775cc4687237e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6655cc150ddc9deba2254780984d0024.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6655cc150ddc9deba2254780984d0024.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f85c133d0a322e4012f7c0eb7f4c626c.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/23/86367bb7-74ca-4052-a1c0-d24f5046afed.png?resizew=244)
(1)如图1,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97cf714ffb3fd5917a76b191640b55fe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c4851109ebad7d40fd6e8c0ed91cde6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fbaeec6b78ac2dce4b20c3fee0139bc6.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/783d872617eed2bbd474035156b6caaf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d15b7c09aac2543b8615aca6b62ee36d.png)
①(1)中的两个结论是否仍然成立?如果成立,请仅就图2的情形进行证明;如果不成立,请说明理由;
②当以点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96e723dd679f5659390e39777911c58c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ff7201050b9d841420f6389dfd4663f.png)
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