1 . 已知数列
前n项和
(
,
为常数).当
的最小值为
时,
的值是
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0ced008e1fe936cf44b403e47bd310bd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b04c7ba0ffd54e60b2829f4440c91ec3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9a8219174fdf7e2954292d8f09cc9ab2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8da45c443af7994a26ffa9d8894e7262.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
A.2 | B.![]() | C.![]() | D.![]() |
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2 . 如图1,
是等边三角形,D.E分别是BC.AC上两点,且
,
与AD交于点H,链接CH.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/2/7f3501ca-4b43-47cf-a058-1727fe890a6a.png?resizew=299)
(1)当
时,求
的值;
(2)如图2,当
时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2fe9e23bc343e7da3426886518e2fa60.png)
__________ ;
__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/387cb1a9bbf3452f9ead3697ce02eb0e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/2/7f3501ca-4b43-47cf-a058-1727fe890a6a.png?resizew=299)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a791da2c892787346863399f2254c48.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a557516283571952c3c3fce82e23d7e.png)
(2)如图2,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f0887929a267fbcc1dc2bee21f455a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2fe9e23bc343e7da3426886518e2fa60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e323760ce16b1e5ade19659f015d89a.png)
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3 . 如图,
,
,
,
,
,则DE等于
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/3/cc639216-6d2d-4e19-a27d-4f4b4afad782.png?resizew=230)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/45acdbac251ca6b76a166c1242e71df9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b6e4a2df58a236c20df5df0d29a466c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/30542b942e3bcbcff9b9fcf75a2b5366.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc11331a7b2d2619b40ee6d34c3bd620.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72f7d9f5e71bfef8188b1216c1276c2d.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/3/cc639216-6d2d-4e19-a27d-4f4b4afad782.png?resizew=230)
A.2 | B.![]() | C.![]() | D.4 |
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