题干

如图,三棱锥P﹣ABC,已知PA⊥面ABC,AD⊥BC于D,BC=CD=AD=1,设PD=x,∠BPC=θ,记函数f(x)=tanθ,则下列表述正确的是(  )

A:f(x)是关于x的增函数

B:f(x)是关于x的减函数

C:f(x)关于x先递增后递减

D:关于x先递减后递增

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答案(点此获取答案解析)

C

同类题2

                           Britain Today
Food
British people like good food, and more than half of them go to a restaurant every month. Fast food is also very popular— 30% of all adults have a hamburger every three months, but
46% have fish and chips!
Sports
British people don’t do a lot of sports. Only 17% of people go swimming every week, about 9% go cycling and 8% play golf—and only 6% of people play football( but 32% go to watch it ).
Cinema and TV
Films are very popular in Britain, and about 60% of people between 15 and 24 go to the cinema every month. At home, men watch TV for about three hours every day — two quarters more than women.
Holidays
British people love going on holiday, and have 56 million holidays every year. Most of these holidays aren’t in the UK—27% are in Spain,10% are in the USA, and 9% are in France. Maybe this is because the weather in Britain isn’t very good!
【小题1】Which food could be more popular among British adults, a hamburger or fish and chips?
A.A hamburger.B.Fish and chips.
C.Both.D.Neither.
【小题2】Which of the followings can show the right percentage (百分比) about Sports in Britain?

【小题3】hose who are interested in movies are ____.
A.menB.women
C.old peopleD.young people
【小题4】How long do British women spend watching TV every day?
A.Three hours.B.Three hours and a half
C.Two hoursD.Two hours and a half
【小题5】 British people’s favorite country for a holiday is ____.
A.SpainB.FranceC.AmericaD.Australia