1 . 如果正整数n满足存在正整数a、b、c使得
,则称n为好数.求证:存在连续2020个正整数这2020个正整数都是好数.
注:对于正整数x,y,
表示x,y的最大公因数.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6e7d94eba88946343c8af9d09408af.png)
注:对于正整数x,y,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/82a79a33a83a7ba57a34b5093d1d1d02.png)
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2 . 如图,已知圆O是
的外接圆,切线
交于点P,D是
的中点,K、L分别在线段
上,且满足
,连结
,求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d79f6bec0d2dab9b9efedfe86d1159b1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0d54431bbb28ebd98db5c1dc6083a75.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6fba0916254a96c1f639f5e82a31ff66.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31c5702fdb97ae60c1fe843d411c309c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5e7ced0f8693546564ff0c3cae34a5b9.png)
![](https://img.xkw.com/dksih/QBM/2021/7/20/2768306466627584/2769064127176704/STEM/c6edafde048243eb9ffac9be34ca1d69.png?resizew=171)
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3 . 如图,已知锐角
的外接圆为
,过B、C分别作圆
的切线交于点P,P在直线
、
、
上的投影分别为D、E、F,
的外接圆与
交于点N(不同于点D),A在
上的投影为M.求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b454cdb97c408300b50d945f002c2cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b454cdb97c408300b50d945f002c2cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72cb97395ebc5ee1b212afb7a97b985c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20a7847bff0073127f10ec3925127414.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/2/2d628892-5769-41da-9d8f-5accddf80b11.png?resizew=178)
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4 . 已知圆
与抛物线
交于A、B、C、D四个不同的点,且
为圆
的直径,线段
和
的中点分别为M、N,求证:线段
在y轴上的投影长度为定值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b454cdb97c408300b50d945f002c2cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/344ccbf79da6ad7e3709d6fa72efb756.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b454cdb97c408300b50d945f002c2cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
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5 . 证明:对任意正整数
,都存在正整数
和
个互不相同的正整数
,使
是完全平方数.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1563da7b0f046a469476668a3686e8f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fe1c31a81f198c443e71b83ca662939.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9cdc0ee2a438b747bf35b7cf4541b0f7.png)
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6 . 如图,在锐角
中,已知点D、E、F分别是点A、B、C在边
、
、
上的投影,
、
的内心分别为
、
,
、
的外心分别为
、
,证明:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9abaeba15f3abdd877bc701af52c5cd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c105d6ba18fbb0581fb982175e2eac9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d7e64c953aaf341e772a5fe776fbc78a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f1ac49b4139636fb1809fe970b23a87.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d1a0fd1ad044a9ecfcba672779bd678.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11d42c1c1ec9ae9cbe441a4f3df06322.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/246140da4fea6ffd1ce81dfca1238cda.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23f919bd3dde10dbbc076f7ec5149699.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c4f6f74444b2b7947fc6e35c8d62322.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f45fb5ae074e506b4e9adfc20608eb4.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/31/bf3c5f9d-c1ca-4897-bc40-aa63e9bf282b.png?resizew=202)
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7 . 如图,在平行四边形
中,
、
分别是边
上的点,线段
、
交于点P,
和
的外接圆的第二个交点Q位于
的内部.证明:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a18722354086c42e62334983fc50eb6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1241216f3c1cb5e73043dd1037f556d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3355e2fa0ac6c675f02ee36c3ced4f2d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24bb49fdc6b6bbb2449fdf8a0de769d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cabe764f05300ac83c7d16b685d27af4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a9a02f2934a771b11ef1b1b5b68776c8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2abc4086606fca8051b61a03bf0d8217.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ac451db3443cabb204f96c31fd4a02e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6772caf1de6f75b00f8d6dcb95f32733.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/16/8ad48411-7ba8-4b21-813e-e816298ecce5.png?resizew=241)
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8 . 已知非空正实数有限集合A,定义集合
,证明:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b65fc3cd4d73993db28934c2584ba44.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/33da439cbb5d0c47765d0009f80fa969.png)
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9 . 已知
证明:存在
,使得
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0c615dcb4f13a1a85ba6ed5725d5946.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cb6ad068c743077c82851d3d51dd9e4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f04583b490faf2ca0c8a3af4f483e1d.png)
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10 . 已知
满足
,E、F分别为
延长线上的点,且
的外接圆与
交于不同于E的点K.证明:点K在
的角平分线上.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5b8b98b2f83279a49e94d9f48c5e6f2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0d54431bbb28ebd98db5c1dc6083a75.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2ef9dbcfa33ca1dde6d73e6bf1e1dc30.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cbce11aa19b8bd2bf6ee5a834e005de.png)
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