如图,在直角三角形
中,
,
,
,垂足为
,则
的值为_____
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcd0ced286a0fbc7e4862f8147264277.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/784d093b48df0ba4ae15ea1368fe85e8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5f215a42c4b7078d8d65923eb9980e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0fe10cd4f9ee205017195dadfd15f9f6.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/7/33dcddaf-bf67-4a81-9d37-49b0e3f49058.png?resizew=108)
更新时间:2019-01-27 13:20:04
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【知识点】 用定义求向量的数量积解读