1 . 在四边形
中,
是四边形
为梯形的___________ 条件.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c8ba2021caf4381dad4f73474912a8d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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2 . 平面上三个力
、
、
共同作用于一点且处于平衡状态,已知
的大小为
,
的大小是
,且
与
的夹角是
,则
与
的夹角大小是________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5076289823db419f94e9c0c8f4aafd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3fb78c5f885034612c0e030b920143d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1282962a17a48a18edf733204054d67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5076289823db419f94e9c0c8f4aafd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf98e72511232b14b841a5d35a607653.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3fb78c5f885034612c0e030b920143d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9aab6a385078abbf793396311122f9d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5076289823db419f94e9c0c8f4aafd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3fb78c5f885034612c0e030b920143d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1e5fa72f2878b476bc57f0df12d6555.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1282962a17a48a18edf733204054d67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5076289823db419f94e9c0c8f4aafd9.png)
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12-13高一上·黑龙江牡丹江·期末
3 . 已知
是平面坐标内三点,其坐标分别为
,
,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91953b03e626b0e1dd5c34392fb692ac.png)
(Ⅰ)求![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fd54baf4bb8742134f9478422f127532.png)
和
大小,并判断
形状;
(Ⅱ)若
为
中点,求
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/516983449108347c9bbf5dd2a72ab3dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9944cdb23cee756ff609d94163b5d08f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3a1ee2752f32f0e3a8d5801ca665f48b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91953b03e626b0e1dd5c34392fb692ac.png)
(Ⅰ)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fd54baf4bb8742134f9478422f127532.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f9ee8474d63b06a57c3cd612c7e87d1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b664f3a011a2f1f31c66a2635c5367c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e428e7a09732be85c1224e9c8f6a71c5.png)
(Ⅱ)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/764509115979e9958101808383672ec0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24c95e61ae9225659dde4c7be4635d96.png)
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