名校
解题方法
1 . 定义
三边长分别为a,b,c,则称三元无序数组
为三角形数.记D为三角形数的全集,即
.
(1)证明:“
”是“
”的充分不必要条件;
(2)若锐角
内接于圆O,且
,设
.
①若
,求
;
②证明:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10a57d1215099fab4a97db12b2fa8f14.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c53315b1196d5a34560cc77995f817d.png)
(1)证明:“
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c53315b1196d5a34560cc77995f817d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7b83cd3d2de78fbc430205d724b8edf.png)
(2)若锐角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a4a9c6bcfb1f63e1e57cccbcfb07e885.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3641602ab775f0425debe0ec778c0ba2.png)
①若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc6dfc6ee5b72469c51c6b5cc44ad72e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0839f7ef584b094ff45fdf01bb8f117e.png)
②证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/90dfb13026887496470c48ed52e46fb0.png)
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