解题方法
1 . 某公园为了美化环境和方便顾客,计划建造一座圆弧形拱桥,已知该桥的剖面如图所示,共包括一段圆弧形桥面ACB和两段长度相等的直线型桥面AD、BE,拱桥ACB所在圆的半径为3米,圆心O在DE上,且AD和BE所在直线与圆O分别在连结点A和B处相切.根据空间限制及桥面坡度的限制,桥面跨度DE的长要不大于18米,不小于12米.已知直线型桥面的修建费用是每米0.6万元,弧形桥面的修建费用是每米2.5万元,设
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/30/fcbe57a7-c0af-45b8-91a8-8e9440d54eb9.png?resizew=204)
(1)若桥面(线段AD,BE和弧ACB)的修建总费用为W万元,求W关于
的函数表达式,并写出
的取值范围;
(2)当
为何值时,桥面修建总费用W最低?(角
的取值精确到
)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc464e9a543e2995cd64ad444f0bf340.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/30/fcbe57a7-c0af-45b8-91a8-8e9440d54eb9.png?resizew=204)
(1)若桥面(线段AD,BE和弧ACB)的修建总费用为W万元,求W关于
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9ea6771d7581e9bfff5f7fa9d43f221d.png)
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2 . 给出函数
,
(1)若
,求不等式
的解集;
(2)若
,且
,求
的取值范围;
(3)若
,非零实数
,
满足
,求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f18cf2aa76c59569a668ee8fb5ae420.png)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b4d795709b0abcf47bceec2250f2f9b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f62acc97e485075f489e1d5e96e09958.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94440d3e4c073f94f2b266ff99d50e74.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/867f0794e209c2aa6dc1ded523427ec7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b4d795709b0abcf47bceec2250f2f9b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea3c5462af41f417a830b88fbad13bbb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01e1d71a91451f7086d9237c0fea607e.png)
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