已知由
,
,
可推得三倍角余弦公式
,已知
,结合三倍角余弦公式和二倍角正弦公式可得![](https://staticzujuan.xkw.com/quesimg/Upload/formula/faa85a9929f03ebeaa6a196e07b7e280.png)
______________ ;如图,已知五角星
是由边长为
的正五边形
和五个全等的等腰三角形组成的,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3921cc68f517e88bb50e61d85bb14f45.png)
___________
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c4cb17b07a5d34718ddb69311352f5bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32eac4b7f177c041219fab18de973c5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a3c0692844acb91c61942d19f39b8d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9eb39658dbb527079675cd8d648458bc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/736770cb37c64f5456331cf4b95bfe2c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/faa85a9929f03ebeaa6a196e07b7e280.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9142a8490de14a87eda628ffa7e28982.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61128ab996360a038e6e64d82fcba004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19ef2d07c67e29fca03640f164efb1e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3921cc68f517e88bb50e61d85bb14f45.png)
![](https://img.xkw.com/dksih/QBM/2021/4/25/2707450330718208/2772467086196736/STEM/aa84574872e740c78f7251230877d563.png?resizew=142)
更新时间:2021-07-26 11:41:38
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