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问题 解答题
已知函数f（x）=2cos2
x
2
-2sin
x
2
cos
x
2
-1，求函数f（x）的最小正周期和值域．
答案

∵f（x）=2cos2

x
2
-2sin
x
2
cos
x
2
-1

=cosx-sinx…2分

=

2
cos（x+
π
4
），…5分

∴T=2π…7分

值域为[-

2
，
2
]…10分

单项选择题

急性 * * 炎的主要病因是

A． * * 破损
B． * * 内陷
C．乳汁淤积
D．首次哺乳
E．乳管堵塞
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单项选择题

Throughout the 19th century and into the 20th, citizens of the United States maintained a bias against big cities. Most lived on farms and in small towns and believed cities to be centres of (1) , crime, poverty and moral (2) Their distrust was caused, (3) , by a national ideology that (4) farming the greatest occupation and rural living (5) to urban living. This attitude (6) even as the number of urban dwellers increased and cities became an essential (7) of the national landscape. Gradually, economic reality overcame ideology. Thousands (8) the precarious (不稳定的) life on the farm for more secure and better paying jobs in the city. But when these people (9) from the countryside, they carried their fears and suspicions with them. These new urbanities, already convinced that cities were (10) with great problems, eagerly (11) the progressive reforms that promised to bring order out of the (12) of the city.

One of many reforms came (13) the area of public utilities. Water and sewerage systems were usually operated by (14) governments, but the gas and electric networks were privately owned. Reformers feared that the privately owned utility companies would (15) exorbitant (过渡的) rates for these essential services and (16) them only to people who could afford them. Some city and state governments responded by (17) the utility companies, but a number of cities began to supply these services themselves. (18) of these reforms argued that public ownership and regulation would (19) widespread access to these utilities and guarantee a (20) price.

2（）

A.disgrace

B.deterioration

C.dishonor

D.degradation
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