1 . 已知单位向量
,
的夹角为60°,向量
,且
,
,设向量
与
的夹角为
,则
的最大值为( ).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05b28baf17059c56ee9ad1ae4814acd8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b04618e5b2db68f2de6ba68972c505c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97169074b37d4b914ecd271e311c0211.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/95842ad442c7f6d5ec4b32939b929e63.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54eff1aaacb1ba98b5e379789f6d47a0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb80eb942aafb194fadc473776f35b1d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05b28baf17059c56ee9ad1ae4814acd8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d66c03d4ca06819a6ce7fc8ea6de0f0.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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2 . 已知为△ABC的内心,且
.记R、r分别为△ABC的外接圆、内切圆半径,若
,则R=____________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/249b81fa939738d06d775a4c97294394.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ecc5ff0f29dbb1816ec2a1e9aa55ee28.png)
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3 . 设点O为三角形ABC内一点,且满足关系式
,则 ![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55d1c51b50b63eb06307d899b04bb630.png)
_____ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/673b8bc2cf72812f05a45b04c23492fd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55d1c51b50b63eb06307d899b04bb630.png)
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