已知,AB、AC为圆O的弦,连接CO并延长,交AB于点D,且∠ADC=2∠C;
(1)如图1,求证:AD=CO;
(2)如图2,取弧BC上一点E,连接EB、EC、ED,且∠EDA=∠ECA,延长EB至点F,连接FD,若∠EDF-∠F=60°,求∠BDF的度数;
(3)如图3,在(2)的条件下,若CD=10,
,求AC的长度.
![](https://img.xkw.com/dksih/QBM/2020/4/10/2438672830611456/2439091674644480/STEM/f2d19256-8dea-47d6-addf-97cb9ab0fb22.png?resizew=492)
(1)如图1,求证:AD=CO;
(2)如图2,取弧BC上一点E,连接EB、EC、ED,且∠EDA=∠ECA,延长EB至点F,连接FD,若∠EDF-∠F=60°,求∠BDF的度数;
(3)如图3,在(2)的条件下,若CD=10,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9d233c752155abe14e96639e166054c.png)
更新时间:2020-04-11 11:27:37
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解答题-证明题
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【推荐1】如图,在平行四边形ABCD 中,E、F 分别是 AD、BC 上的点,连接 AF、CE,且 AF∥CE.
![](https://img.xkw.com/dksih/QBM/2020/2/28/2415795700629504/2433581390905344/STEM/d3663e46cb9c4d488d226c35dbcfa291.png?resizew=132)
求证:∠BAF=∠DCE.
![](https://img.xkw.com/dksih/QBM/2020/2/28/2415795700629504/2433581390905344/STEM/d3663e46cb9c4d488d226c35dbcfa291.png?resizew=132)
求证:∠BAF=∠DCE.
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【推荐2】如图,在四边形ABCD中,AB∥CD,AB=AD,CB=CD,点E是CD上一点,连接BE交AC于点F,连接DF
(1)求证:四边形ABCD是菱形;
(2)试探究BE满足什么条件时,∠EFD=∠BCD,并说明理由.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/4/3/b1d56c24-6d84-44e2-972c-19e10c8c5d14.png?resizew=175)
(1)求证:四边形ABCD是菱形;
(2)试探究BE满足什么条件时,∠EFD=∠BCD,并说明理由.
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适中
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【推荐1】已知正方形
,点
,
分别是边
,
上的动点.
,
分别是边
,
上的中点,证明
;
(2)如图②,若正方形
的边长为1,
的周长为2,证明
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7faabc484ce3666706c1beffda4bcfe2.png)
(2)如图②,若正方形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f2ea13010e2399194be2a681310543e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/345c91c9e67e6ee00a872078ab17f094.png)
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【推荐2】如图,已知
中,
,点
、
分别在
、
上,且
,如何说明
呢?
![](https://img.xkw.com/dksih/QBM/2020/9/7/2544435558424576/2546597659189248/STEM/4169d637e2f041a2b2423553ac8a4542.png?resizew=204)
解:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c4046f62f73ca345f5ad182fc0c71e0.png)
( )
又
( )
( )
( )
( )
( )
( ).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dc9795efa99b6fb9fdf9778085dab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](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/421291381be28da4bd16560fd383b4a9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49c8dbc31b2e14067ef2f34b4e25f114.png)
![](https://img.xkw.com/dksih/QBM/2020/9/7/2544435558424576/2546597659189248/STEM/4169d637e2f041a2b2423553ac8a4542.png?resizew=204)
解:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c4046f62f73ca345f5ad182fc0c71e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f162eb627de59b28702b5593e82b530f.png)
又
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eacf0012f7d355e89757dcd8871876a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8335d0b4d053aff2899644578793ba79.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/799090c434cf4c42aaa143b6661915cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54bb3caba2b157026325b3d8a5404fc8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9f617fa80f09fc245909492f5335ea5c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2444fdccd9d7272195635c0d0db642dd.png)
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【推荐1】如图,在平行四边形
中,
的平分线
交
于点E,
的平分线
交
于点F,
与
相交于点O,连接
.
是菱形;
(2)若
,求平行四边形
的面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2947ca8e0cdbeb4aab80ce9e7b63ba98.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d39b8d91afc34e4a9b0fdbb6bafb9087.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/274cf35acb4a1748d15c39d15a9bea7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/274cf35acb4a1748d15c39d15a9bea7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2dde327febef2331a4766a79b433cc02.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1f5b3ae6d6218592b129ff915552fbc0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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【推荐2】如图,在
中,
,CD平分
交AB于点D,将
绕点C逆时针旋转到
的位置,点F在AC上,连接DE交AC于点O.
(1)求证:
;
(2)若
,
.求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed10df4140819d5451773a45de66201b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8fabb884dc5f9609de491245463bbe9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f15ba851a0f65c271ec774095516f07.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f4aa6359e027e952a897435224044db.png)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f3aa1da9eef031c9562154530cbafb33.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ebf4d515537e761d6fe49119b51d76c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f656e1d1f68954e5f06de8958f6a9310.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
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解答题-证明题
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【推荐1】如图,
是半圆O的直径,C为半圆O上的点(不与A,B重合),连接
,
的角平分线交半圆O于点D,过点D作
的垂线,垂足为E,连接
交
于点F.
![](https://img.xkw.com/dksih/QBM/2022/12/16/3132155867471872/3133571645652992/STEM/85f7025457944c2b881ad4b05e2bfbf2.png?resizew=174)
(1)求证:
是半圆O的切线;
(2)若
,
,求半圆O的半径及
的长.
![](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/7cbce11aa19b8bd2bf6ee5a834e005de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://img.xkw.com/dksih/QBM/2022/12/16/3132155867471872/3133571645652992/STEM/85f7025457944c2b881ad4b05e2bfbf2.png?resizew=174)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/86338536656046e93b53672ade9a78b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d4746df85049d1651d3f6c30212a7a9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aa2b5e09f8ec785c59900a529390a02.png)
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【推荐2】如图,⊙O为
的外接圆,
为⊙O的直径,C是
延长线上一点,且
.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/4/3/88b17cb1-f0e4-4215-8818-7a95edb0d5ad.jpg?resizew=139)
(1)求证:
为
的切线;
(2)若
,
,求
的半径.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab2a2834d80ff574e79eae8ca8d4e94f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2bfbc2f50c2464e04e400bc63ec2236.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/4/3/88b17cb1-f0e4-4215-8818-7a95edb0d5ad.jpg?resizew=139)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c279c8033acb94c3f91be2e05b0a6bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55c24a968c73e960698a572ab01e3698.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
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