搜题请搜索小程序“爱下问搜题”
问题 解答题
已知函数f(x)=
3
sin(ωx)-2sin2
ωx
2
（ω＞0）的最小正周期为3π，
（Ⅰ）当 x∈[
π
2
， 
3π
4
]时，求函数f（x）的最小值；
（Ⅱ）在△ABC，若f（C）=1，且2sin2B=cosB+cos（A-C），求sinA的值．
答案

f(x)=

3
sin(ϖx)-2•
1-cos(ϖx)
2
=
3
sin(ϖx)+cos(ϖx)-1=2sin(ϖx+
π
6
)-1

依题意函数f（x）的最小正周期为3π，即

2π
ϖ
=3π，解得ϖ=
2
3
，

所以f(x)=2sin(

2
3
x+
π
6
)-1

（Ⅰ）由

π
2
≤x≤
3π
4
得
π
2
≤
2
3
x+
π
6
≤
2π
3
，

所以，当sin(

2
3
x+
π
6
)=
3
2
时，f(x)最小值=2×
3
2
-1=
3
-1

（Ⅱ）由f(C)=2sin(

2C
3
+
π
6
)-1及f（C）=1，得sin(
2C
3
+
π
6
)=1

而

π
2
≤
2
3
C+
π
6
≤
2π
3
，所以
2
3
C+
π
6
=
π
2
，解得C=
π
2

在Rt△ABC中，∵ A+B=

π
2
，2sin2B=cosB+cos（A-C）2cos2A-sinA-sinA=0，

∴sin2A+sinA-1=0，解得sinA=

-1±
5
2
∵0＜sinA＜1，∴ sinA=
5
-1
2

阅读理解

.

第二部分：阅读理解（共25小题，每题2分，满分50分）

第一节选择题（共20小题，每题2分，满分40分）

阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。

Getting around in Canada is fairly easy. Most cities have urban transportation systems, including buses, streetcars, and trains, and some of the larger cities also have subways. You can board these systems at regular stops along their routes. Some let you pay with cash while others require tickets. If you don’t have a ticket for the bus, you must pay with the correct amount of money. This is because the driver does not carry any change. If you plan to stay in a city for a long time, you may want to buy a monthly pass or a package of tickets to save money. You can buy subway tickets at any subway station.

If you have to take several buses or subways for a single trip, you do not need to pay money each time. Simply ask the driver for a transfer (换乘) ticket, or take one from the machines on the subway platform.

If you are not sure where to board the bus or the streetcar, just ask someone or follow the crowd. People can usually only board at the front of the bus where you show your pass to the driver. When using public transportation, Canadians line up. First come, first serve, is a common approach to many activities in Canada, and it is considered to be extremely rude to cut in any line.

Maps of routes and schedules are usually available from the public transit (运输) company in your area, and there is also a telephone information line. You may ask someone for the name of the transit company in your area, and then look it up in the telephone book.

46. What is this passage mainly about?

A. How to use public transportation in Canada.

B. How to save money when traveling.

C. Where to find subways in larger cities.

D. How public transit companies work.

47. If you pay the bus fare in cash, _____.

A. you may be given some change

B. you can exchange money with the driver

C. it might cost you a little more

D. you must have the exact amount of money

48. By buying a monthly pass or a package of tickets, you can ______.

A. take a bus whenever you want      B. go wherever you like

C. save money                     D. find comfortable seats

49. If you have to change subway lines on a single trip, _____.

A. you have to pay each time

B. you should buy another ticket from the machine

C. you must ask for the driver’s permission

D. you just need to pay once
查看答案
问答题

阅读资料，联系实际，请就资料9中所提到的政府采购制度阐述一下自己的观点，并结合国外政府采购制度的先进经验，谈一谈进一步完善政府采购制度的措施。 [要求] 针对性强，条理清晰，不超过500字。
查看答案