1 . 设
是单位向量,
,则四边形
是( ).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c984376f5475184e0d3e4f7e1bb65f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c1aef4c06a9b56641473587a88c354c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
A.梯形 | B.无特殊限制的菱形 | C.正方形 | D.无特殊限制的矩形 |
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9-10高一下·福建宁德·期末
2 . 对于菱形ABCD,给出下列各式:①
;②
;③
④
,其中正确的个数为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0f134605b8b48aaebce5ebfc06b7467.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f3b82e1e4e331a7a17c9d8a7a5852c3f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/496986cbe96166c65c217a26a9f1309f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c01c35af7e8ce3b1098bdbf123a63a24.png)
A.1个 | B.2个 | C.3个 | D.4个 |
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