如图,从B点测得塔顶A的仰角为60°,测得塔基D的仰角为45°,已知塔基高出测量仪器20米(即DC=20米),求塔身AD的高(精确到1米).
![](https://img.xkw.com/dksih/QBM/2013/3/12/1573611607506944/1573611639218176/STEM/0c9dd955ee63481fa591af87e3577d58.png)
更新时间:2016-12-05 16:23:59
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【知识点】 初中数学综合库
相似题推荐
解答题-证明题
|
适中
(0.65)
名校
【推荐1】如图,已知
是
的直径,
与
相切于C,过点B作
,交
延长线于点E.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/11/64940c3c-733a-4b9a-867e-96047f7acb58.png?resizew=191)
(1)求证:
是
的平分线;
(2)若
,
的半径
,求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](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)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c38bbe49284a2ceab26001ced8cfd56.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/11/64940c3c-733a-4b9a-867e-96047f7acb58.png?resizew=191)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2cfc2771aa0d5b97d2297f8a26a6f6b1.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ead1eda1ca5b67586379a09a4c3540b1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/434845564fd5765244f8d1aa9240fa39.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
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解答题-证明题
|
适中
(0.65)
【推荐2】有一些代数问题,我们也可以通过几何方法进行求解,例如下面的问题:
已知:
,求证:
.
经过思考,小明给出了几何方法的证明,如图:
①在直线
上依次取
,
;
②以
为直径作半圆,圆心为
;
③过
点作直线
的垂线,与半圆交于点
,连接
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/14/ad03fb29-16f5-4eb8-9445-a113d174726e.png?resizew=225)
请回答:
(1)连接
,
,由作图的过程判断,
,其依据是 ;
(2)根据作图过程,试求线段
、
(用
,
的代数式表示),请写出过程;
(3)由
,可知
,其依据是 ,由此即证明了这个不等式.
已知:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a0c4c098615c6bc7e6dcf72e5b5201a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ef4862577ef4d87d0cff2165fe39bb6.png)
经过思考,小明给出了几何方法的证明,如图:
①在直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d42e97eee705d164e6ac6de9ecd6d1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a4a88b719166fcc1431f876bc8c5656c.png)
②以
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
③过
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/683c590673eece14fea3319c4fd5eb55.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/14/ad03fb29-16f5-4eb8-9445-a113d174726e.png?resizew=225)
请回答:
(1)连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4795ee1f96b430529934e2231b38885d.png)
(2)根据作图过程,试求线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/683c590673eece14fea3319c4fd5eb55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
(3)由
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70734a8e672376bb0bd1522e229f86a2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d251eb8546c1afbe3701679eff7f7e65.png)
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