已知f（x）=2x2+1，则函数f（cosx）的单调减区间为______．_爱下问搜题

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问题填空题

已知f（x）=2x²+1，则函数f（cosx）的单调减区间为______．

答案

解；∵f（x）=2x²+1，

∴f（cosx）=2cos²x+1

=1+cos2x+1

=cos2x+2，

令2kπ≤2x≤2kπ+π，k∈Z．

解得kπ≤x≤kπ+

π

2

，k∈Z．

∴函数f（cosx）的单调减区间为[kπ，

π

2

+kπ]，k∈Z．

故答案为：[kπ，

π

2

+kπ]，k∈Z．

综合

旅游地理阅读材料，回答下列问题。(10分)

敦煌研究院作过统计，每年从5月到10月份，莫高窟每天的游客平均保持在3 000人到5 000人。而科学的测算结果表明，合理的游客承载量应该是每天2 900多人。

甘肃省敦煌地区旅游景点分布图

(1)请说出敦煌地区有哪些自然旅游景观。

(2)结合材料评价敦煌地区旅游资源的开发条件。

完形填空

My best friend is one of my classmates. We have the     hobby. We both enjoy music. I am good      English, but she isn’t. She has great interest in university (大学) life and wants to go to university when she     school. One day, I found her studying     so I wanted to help her with it.     she closed (关上) the book. I asked, "What are you doing?"
"Nothing," she answered shyly. I didn’t know      she closed her book. "I just want to     you," I said. "Please don’t laugh at me. My English is not good and I’m a little     about learning it in front of others."
"      laughs at you. That’s why you don’t make any progress (进步) in English. You should try. You should do your best to     English with your friends. You can also ask for help from them."

A．wild(狂野的)

C．calm(镇静的)