你见过树木的年轮吗?从树木的年轮,可以知道树木的年龄.把树干的横截面看成是圆形的,如果一棵20年树龄的树的树干直径是
,这棵树的半径平均每年增加多少?
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b713629a795d5229343def83d571597.png)
![](https://img.xkw.com/dksih/QBM/2021/10/2/2820872553799680/2820906758938624/STEM/bb6deab62d3e4dcfa7cf7567d5a7f879.png?resizew=94)
21-22九年级上·全国·课后作业 查看更多[2]
更新时间:2021-10-02 22:12:24
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解答题-证明题
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较易
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【推荐1】如图,已知
、
是
的两条弦,且
,D是
延长线上一点,连接
并延长交
于点E,连接
并延长交
于点F.求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
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解答题-问答题
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【推荐2】如图,在⊙O中,AB为弦,C、D在AB上,且AC=BD,请问图中有几个等腰三角形?把它们分别写出来,并说明理由.
![](https://img.xkw.com/dksih/QBM/2018/1/1/1851185792491520/1857909977751552/STEM/5e807d38346046749cc278f04fa3cabc.png?resizew=138)
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