解题方法
1 . 某校团委组织开展了知识竞赛活动.现有两组题目放在A,B两个信封中,A信封中有6道选择题和3道论述题,B信封中有3道选择题和2道论述题.参赛选手先在任一信封中随机选取一题,作答完后再在此信封中选取第二题作答,答题结束后将这两个题目放回原信封.
(1)若同学甲从B信封中抽取了2题,求第2题抽到论述题的概率;
(2)若同学乙从A信封中抽取了2题,答题结束后误将题目放回了B信封,接着同学丙从B信封中抽取题目作答,已知丙取出的第一个题是选择题,求乙从A信封中取出的是2个论述题的概率.
(1)若同学甲从B信封中抽取了2题,求第2题抽到论述题的概率;
(2)若同学乙从A信封中抽取了2题,答题结束后误将题目放回了B信封,接着同学丙从B信封中抽取题目作答,已知丙取出的第一个题是选择题,求乙从A信封中取出的是2个论述题的概率.
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解题方法
2 . 如图,在高为2的正三棱柱
中,
是棱
的中点.
(2)求三棱锥
的体积;
(3)设
为棱
的中点,
为棱
上一点,求
的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78490ad8408d831761e8ebdafa25978c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
(2)求三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c8ce034f2d6b7ac835ce46d58ea945ec.png)
(3)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/56f7ba05c54b3de1f4378f7c8eb58328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0a851907ada2ac2c3c4880a6736d28a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d022b233edaffb56b84d53bac243e1c6.png)
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3 . 在
中,
.
(1)证明:
为
的重心.
(2)若
,求
的最大值,并求此时
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17bd00f21e9ace05db352d22af5013c6.png)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc7064d10d2f23ab4066b87e2f0e9171.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7e00dca7e69aecb730b9f2ba0774a053.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
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解题方法
4 . 如图,在四棱锥
中,
底面![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6accb9d9ec3fe4ffb5ad146a52069081.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/638537c0a30676c73fea76c80e0f8bd0.png)
,
,点
为棱
的中点.![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
平面
;
(2)求三棱锥
的体积;
(3)求直线
与平面
所成角的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6accb9d9ec3fe4ffb5ad146a52069081.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/638537c0a30676c73fea76c80e0f8bd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0409adbc827b03d1fa3a58ef1a2e0880.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/638537c0a30676c73fea76c80e0f8bd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/852aabd89edffc1b94344ff3f1f31ccd.png)
(2)求三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb7ed85b76fb4c5e9a9a60bff4337742.png)
(3)求直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20a541b81584a032f571159ea152c85a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c09afc70f448545336304333d5b5658b.png)
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5 . 已知
.且
,函数
的最小正周期为
.
(1)求函数
的解析式与单调递增区间;
(2)在锐角
中,内角
的对边分别是
,点
在
上,且
平分
,求
的周长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb340a5e9b1aa6b8c9ec9f034e23ad05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8bf21fef3026cfe445a855c94cab5c84.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d275fbb3ee5cd1177ca5a2ceecbbef0f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed2d1ecae9c649cc3c89f9ce0c063208.png)
(1)求函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d275fbb3ee5cd1177ca5a2ceecbbef0f.png)
(2)在锐角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e428e7a09732be85c1224e9c8f6a71c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24e0c10fb103930eabd5fa18e8f9bb06.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/adf9899f990f4bf09d39c7bd42c5d9bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b2b425bf3f0e9eab16495e161a1655a0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e428e7a09732be85c1224e9c8f6a71c5.png)
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解题方法
6 . 设
的内角
的对边分别为
,且
.
(1)求角
的大小;
(2)若
,角
的平分线交
边于
,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24e0c10fb103930eabd5fa18e8f9bb06.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4317e7917b4a32d538469506f5c40639.png)
(1)求角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a2d1973cd9f92fd15946d6d34452f0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/27a65a740900ed21397f516cda4a58b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c163a189c44fd9e9234bedd4dd96625c.png)
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解题方法
7 . 如图,△ABC与△DBC所在平面垂直,且
,
.
;
(2)求直线BC与平面ABD所成角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bca76d0d2614f113bcd4c9e134b95123.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f95c3a9f27b8f6766aafda84ebefa736.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76d72a007e3c4a134956b0e3fbde5f46.png)
(2)求直线BC与平面ABD所成角的余弦值.
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解题方法
8 . 在
中已知
.
(1)求
;
(2)若
面积为
,求
的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0616c80eda75596677ffc3ed8181deef.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c32e2f2d7147cf1699fbfdef9cf4af74.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e428e7a09732be85c1224e9c8f6a71c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/704f858f73063183e5779257900e694d.png)
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9 . 如图,在圆锥
中,
为圆锥顶点,
为圆锥底面的直径,
为底面圆的圆心,
为底面圆周上一点,四边形
为矩形.
平面
;
(2)若
,
,
,求平面
和平面
夹角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/71b63d2504bd3ecce8c10560b142356f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/612d205b9f558fef350ad20ee3a0a61d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2ffc6952e988d04f22f0fb2f7f0ab7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c66d99a6a8415ddad22bbed33b64cfb.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/41367d5c13d47c3524390cb192f2f118.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/890c3adc2db9d97a4353a5abaccd6519.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5f5f5b197e7864c92e66eaaadd24e33.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9a32bd7a1b78b5a0ec562c4025aea8c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10fc7991ea17d54ff5f4445ac5699463.png)
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10 . 近些年来,由于手机与电脑的影响,学生视力问题逐渐突出.习近平总书记作出重要指示,呵护好孩子的眼睛就是呵护孩子的未来.为了落实这一指示,某学校调查了学生的视力情况,随机抽取了200名学生,男生80人,女生120人,记录了他们的视力情况,结果如下表:
(1)是否有90%的把握认为近视与性别有关(结果精确到0.001);
(2)从120名女生中按是否近视,采用分层抽样的方法抽取12人,再从12人中随机抽取4人做进一步调查,记抽到一名近视的得
分,抽到一名不近视的得1分,设随机变量X表示抽取的4名学生的总得分,试求X的分布列与数学期望
.
附:独立性验临界值表
公式
,其中
.
近视 | 不近视 | |
男生 | 50 | 30 |
女生 | 70 | 50 |
(2)从120名女生中按是否近视,采用分层抽样的方法抽取12人,再从12人中随机抽取4人做进一步调查,记抽到一名近视的得
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acbc6a613224461ade69362d46550474.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9fc79c66ebaacd709ec9965b90a22b14.png)
附:独立性验临界值表
P![]() | 0.1 | 0.05 | 0.01 | 0.005 | 0.001 |
![]() | 2.706 | 3.841 | 6.635 | 7.879 | 10.828 |
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f503f0dec4cf2cc95ad9521c5eaf9f18.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/356b05e46b10ee51c3e43546d73ec96c.png)
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